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Centers for Disease Control and PreventionDavid J. Sencer CDC Museum
Tom Harkin Global Communications Center June 4-8, 2012
Teach EpidemiologyProfessional Development Workshop
Day3
2
3Teach Epidemiology
Teach Epidemiology
4
Time Check
8:15 AM
5
6Teach Epidemiology
Teach Epidemiology
Teach Epidemiology Workshop—Day 2
Diane Marie M. St. George, PhDUniversity of MD School of Medicine
Back to EU 2 and 3
Why study patterns of disease? Why is a description of the person, place, and time elements of a disease distribution important?
Epidemiologic Studies
• Descriptive epidemiology– Describes patterns of disease– Suggests hypotheses about relationships between
“exposures” and “health-related conditions”
• Analytic epidemiology– Tests hypotheses– Evaluates relationships– Always in a search for causality– Knowing causation helps us to prevent and treat
disease and promote health
Enduring Understandings
4. A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated.
5. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed.
6. When an exposure is hypothesized to have a detrimental effect, it is not ethical to intentionally expose a group of people. In these circumstances, studies can be designed that observe groups of free-living people with and without the exposure.
Testing hypotheses about BrCA
• Hypothesis: High dietary fat intake increases risk of BrCA.
• Evaluate the hypothesis using a:
– Case-control study
Case-control study of dietary fat and BrCA
• Exposure is diet– Measured as dietary fat intake (FFQ)
• Outcome is BrCA– Measured as yes or no
• Want to ensure that you have enough cases to do your study, so recruit participants with BrCA
• Find those without BrCA• Ask them about diet• What might you expect to see?
Diet and BrCA
BrCA+ BrCA-
High fat
Low fat
100 100 200
Diet and BrCA
BrCA+ BrCA-
High fat 60 10 70
Low fat 40 90 130
100 100 200
What is the prevalence of BrCA?
Case-control Study
• Odds = probability an event will occur/probability that an event will not occur
• Odds of exposure in cases = (among cases) probability of being
exposed/probability one was not exposed• What is odds of exposure in controls?= (among controls) probability of being exposed/
probability one was not exposed• What is Odds Ratio?
Diet and BrCABrCA+ BrCA-
High fat 60 10 70
Low fat 40 90 130
100 100 200
What is the odds of exposure among the cases?
What is the odds of exposure among the controls?
What is the OR?
Diet and BrCA
BrCA+ BrCA-
High fat 60 10 70
Low fat 40 90 130
100 100 200
What is the odds of exposure among the cases? (60/100)/(40/100) = 60/40 = 1.5
What is the odds of exposure among the controls? (10/90) = .11
What is the OR? ~ 13.5
Case-control Study
• Key elements– Compare individuals selected on the basis of disease status– Classic epidemiologic study design
• Quantify association– Odds Ratio
• Advantages – Can be less expensive and time-consuming than follow-up studies– Efficient for rare diseases
• Disadvantages – May be resource-intensive because of need to screen so many– Difficult to assess temporality
Testing hypotheses about BrCA
• Hypothesis: High dietary fat intake increases risk of BrCA.
• Evaluate the hypothesis using a:
– Cohort study
Cohort study of diet and BrCA
• Exposure is diet– Measured with food diary
• Outcome is BrCA– Measured as yes or no
• Want to ensure that you have enough exposed persons to do your study, so select for those with high fat intake
• Find those with low fat intake• Follow them up over time to ascertain BrCA status• What might you expect to see?
Diet and BrCA
BrCA+ BrCA-
High fat 100
Low fat 100
200
Diet and BrCA
BrCA+ BrCA-
High fat 70 30 100
Low fat 35 65 100
105 95 200
What is the incidence of BrCA among those with high fat intake?
What is the incidence of BrCA among those with low fat intake?
What is the risk ratio?
Diet and BrCA
BrCA+ BrCA-
High fat 70 30 100
Low fat 35 65 100
105 95 200
What is the incidence of BrCA among those with high fat intake? = 70%
What is the incidence of BrCA among those with low fat intake? = 35%
What is the risk ratio? = 2.0
Cohort Study
• Key element– Select based on exposure status and follow-up over time
• Quantify association– Relative risk (risk ratio)
• Advantages– Minimizes confusion about temporality– Ideal for rare exposures
• Disadvantages– May have to screen many to get exposed group– Large, time-consuming, expensive especially if disease is relatively rare
and/or slow to develop– Inefficient for rare diseases
Testing hypotheses about BrCA
• Hypothesis: High dietary fat intake increases risk of BrCA.
• Evaluate the hypothesis using a:
– Randomized controlled trial
RCT study of diet and BrCA
• Exposure is diet– Measured as dietary fat exposure
• Outcome is BrCA– Measured as yes or no
• Want to ensure maximal control over study parameters, so you decide who gets exposed and who does not
• Follow up over time to ascertain BrCA status• What might you expect to see?
Diet and BrCA
BrCA+ BrCA-
High fat
Low fat
200
Diet and BrCA
BrCA+ BrCA-
High fat 70 30 100
Low fat 35 65 100
105 95 200
What is the incidence of BrCA among the high fat group?
What is the incidence of BrCA among the low fat group?
What is the risk ratio?
Diet and BrCA
BrCA+ BrCA-
High fat 70 30 100
Low fat 35 65 100
105 95 200
What is the incidence of BrCA among the high fat group? = 70%
What is the incidence of BrCA among the low fat group? = 35%
What is the risk ratio? = 2.0
Randomized Controlled Trial
• Key elements– Assign treatments to individuals and follow up to ascertain disease status.– The researcher controls primary exposure under study. Exposures can be
treatments (drug, surgery) or preventive measures (water fluoridation, exercise regimens).
– Ethical considerations may preclude use of this design.• Quantify association
– Relative risk (risk ratio)• Advantages
– Random assignment serves to “equate” groups– Closest to “true experiment”
• Disadvantages– Expensive and time-consuming– Subjects are often highly selected group because the requirements of
participants can often be extensive
31
Time Check
9:45 AM
32
33Teach Epidemiology
Teach Epidemiology
34
35
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
36
Association Found Between Coffee and Pancreatic Cancer
Associated
Teach Epidemiology
37
What do we mean when we say that there is an association between two things?
Associated
Tied Related
Linked
Things that are associatedare linked in some way that makes them
turn up together.
Associated
Teach Epidemiology
38
Things that are associated are linked in some way that makes them turn up
together.
Associated
Teach Epidemiology
39
Suicide Higher in Areas with Guns
Smoking Linked to Youth Eating Disorders
Snacks Key to Kids’ TV- Linked Obesity: China Study
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Breakfast Each Day May Keep Colds Away
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Depressed Teens More Likely to Smoke
Associated
Teach Epidemiology
40
Epidemiologic studies that are concerned with characterizing the amount and distribution of
health and disease within a population.
Descriptive Epidemiology
Teach Epidemiology
41
Epidemiologic studies that are concerned with determinants of disease and the reasons for relatively high or low
frequencies of disease in specific population subgroups.
Analytical Epidemiology
Teach Epidemiology
42
Hypothesis
Formulating
Descriptive Epidemiology
Testing
Analytical Epidemiology
An unproven idea, based on observation or reasoning, that can
be supported or refuted through investigation
An educated guess
Hypothesis
Teach Epidemiology
43
44
Making Group Comparisons and Identifying Associations
Teach Epidemiology
45
Hypothesis:
Buprenorphine will stop heroin addicts from using heroin.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
46
PopulationTrial 1
Making Group Comparisons and Identifying Associations
47
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
Trial 1
Making Group Comparisons and Identifying Associations
48
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
21 Heroin Addicts Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
49
Bupe
Tested Positive for Heroin Total
10021 79
Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
Teach Epidemiology
50
When you can measure what you are speaking about, and express it in numbers,
you know something about it.
Lord Kelvin
But when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
51
A measure of how often an outcome occurs in a
defined population in a defined period of time. It consists of a
numerator and a denominator.
Risk
The numerator is the number of people in the population or
sample who experienced the outcome and the denominator is the total number of people in the
population or sample.
Population / Sample
Outcome
Denominator
Numerator
Making Group Comparisons and Identifying Associations
Teach Epidemiology
52
… the risk of a negative heroin test was 21 / 100 in a 10-week period
21 tested negative for
heroin 100 study subjects
Numerator
Denominator
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
53
A measure of how often an outcome occurs in a defined group of people
in a defined period of time.
The likelihood of an outcome occurring.
Risk / Rate
Making Group Comparisons and Identifying Associations
Teach Epidemiology
54
Trial 1
Bupe
Tested Positive for Heroin
10021 79
Tested Negative for Heroin
21
100or 21 %
Calculating Risk
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
55
Process of predicting from what is observed in a sample to what is true for the entire population.
Inference
Making Group Comparisons and Identifying Associations
Teach Epidemiology
56
Trial 1
What does this tell you about the hypothesis?
Buprenorphine will stop heroin addicts from using heroin.
InferenceProbe
Bupe
Tested Positive for Heroin
10021 79
Tested Negative for Heroin
21
100or 21 %
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
57
People who participate in a trial, but do not get the treatment.
People whose results are compared to the group that was treated.
Control Group
Making Group Comparisons and Identifying Associations
Teach Epidemiology
58
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Control Group
Extend and label the table to include a control group.
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
59
100?
100or ? %No Bupe
Control Group
Making Group Comparisons
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
60
100?
100or ? %No Bupe
Making Group Comparisons
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Exposure
Outcome / Disease
a b
c d
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
61
21
100or 21 %
Total
1007921Bupe
100?
100or ? %No Bupe
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Making Group Comparisons and Identifying Associations
Teach Epidemiology
62
A cross-classification of data where categories of one variable
are presented in rows and categories of another variable
are presented in columns
The simplest contingency table is the 2x2 table.
Contingency Table
Making Group Comparisons and Identifying Associations
Teach Epidemiology
63
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
21 Heroin Addicts Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
64
Trial 2
Total
?
100? %
a b
c d
Bupe
Tested Negative for Heroin
Tested Positive for
Heroin
No Bupe 100
100?
100? %
Risk of
Negative Heroin
Test
Making Group Comparisons and Identifying Associations
Teach Epidemiology
65
E
Assigned
E
O
O
O
O
Making Group Comparisons and Identifying Associations
Volunteer Heroin Addicts
Teach Epidemiology
66
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Probe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Making Group Comparisons and Identifying Associations
Teach Epidemiology
67
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Making Group Comparisons and Identifying Associations
Teach Epidemiology
68
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
Making Group Comparisons and Identifying Associations
Teach Epidemiology
69
When you can measure what you are speaking about, and express it in numbers, you know something about it.
Lord Kelvin
But when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
70
The value obtained by dividing one quantity by another
Ratio
Making Group Comparisons and Identifying Associations
Teach Epidemiology
71
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Ratio: The value obtained by dividing one quantity by another
Risk Ratio: The ratio of two risks
1
Risk Ratio
Making Group Comparisons and Identifying Associations
Teach Epidemiology
72
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Ratio: The value obtained by dividing one quantity by another
Risk Ratio: The ratio of two risks
1
Risk Ratio
Create a formula
a
a + b
c
c + d
Making Group Comparisons and Identifying Associations
Teach Epidemiology
73
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
1
Risk Ratio
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
Relative Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
74
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
1
Risk RatioRelative Risk
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
The inference here is that there is no effect of Buprenorphine
Making Group Comparisons and Identifying Associations
Teach Epidemiology
75
Trial 3
?
100? %100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
?
100? %100 or
Making Group Comparisons and Identifying Associations
Teach Epidemiology
76
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
77
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
78
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
79
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
0.34
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
80
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
0.34
The heroin addicts who received Bupe were ___ times as likely to test negative for heroin as those who did not receive Bupe.
0.34
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
81
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
0.34
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population.
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
82
Trial 4
?
100? %100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
?
100? %100 or
Making Group Comparisons and Identifying Associations
Teach Epidemiology
83
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
84
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
85
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
3.5
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
86
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
3.5
The heroin addicts who received Bupe were ___ times as likely to test negative for heroin as those who did not receive Bupe.
3.5
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
87
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
3.5
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population.
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
88
21
10021%21 79 100 orBupe
Trial 1
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
What do the results tell us about the hypothesis that Buprenorphine will stop heroin addicts from using heroin?
Nothing
Making Group Comparisons and Identifying Associations
Teach Epidemiology
89
Trial 1 Trial 2
Trial 3 Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
90
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
100
Making Group Comparisons and Identifying Associations
Teach Epidemiology
91
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
100
Making Group Comparisons and Identifying Associations
Teach Epidemiology
92
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
Making Group Comparisons and Identifying Associations
Teach Epidemiology
93
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
1
Bupe is not associated with having a negative test for heroin.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
94
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative test for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
Making Group Comparisons and Identifying Associations
Teach Epidemiology
95
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative test for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
Making Group Comparisons and Identifying Associations
Teach Epidemiology
96
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative test for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
Nothing
Compared to what?
Making Group Comparisons and Identifying Associations
Teach Epidemiology
97
Buprenorphine
Buprenorphine & Naloxone
Placebo
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Handout
98
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
99
Time Check
10:30 AM
100
101Teach Epidemiology
Teach Epidemiology
102
Time Check
10:45 AM
103
104Teach Epidemiology
Teach Epidemiology
105
Suicide Higher in Areas with Guns
Smoking Linked to Youth Eating Disorders
Snacks Key to Kids’ TV- Linked Obesity: China Study
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Breakfast Each Day May Keep Colds Away
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Depressed Teens More Likely to Smoke
In the News
106
Total
a b
dc
2 x 2 Table
Suicide Higher in Areas with Guns
107
Total
a b
dc
People who are exposed
a b
2 x 2 Table
Suicide Higher in Areas with Guns
Areas with Guns
No SuicideSuicide
Areas without Guns
108
a b
dc
2 x 2 Table
Total
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
109
a b
dc
2 x 2 Table
R-Rated Movies
TotalDrink & Smoke
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
No Drink & Smoke
No R-Rated
Movies
110
a b
dc
People who are exposed and have the outcome
a
2 x 2 Table
R-Rated Movies
TotalDrink & Smoke
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
No Drink & Smoke
No R-Rated
Movies
111
a b
dc
2 x 2 Table
Family Meals Are Good for Mental Health
Total
112
a b
dc
2 x 2 Table
Family Meals Are Good for Mental Health
Family Meals
TotalMental Health
No Mental Health
No Family
Meals
113
a b
dc
People who are not exposed and do not have the outcome
d
2 x 2 Table
Family Meals Are Good for Mental Health
Family Meals
TotalMental Health
No Mental Health
No Family
Meals
114
a b
dc
2 x 2 Table
Study Links Iron Deficiency to Math Scores
Total
115
a b
dc
2 x 2 Table
Study Links Iron Deficiency to Math Scores
Iron Deficiency
Poor Math
Scores
No Iron
Deficiency
Good Math
Scores Total
116
a b
dc
People who do not have the outcome and are not exposed
d
2 x 2 Table
Study Links Iron Deficiency to Math Scores
Iron Deficiency
Poor Math
Scores
No Iron
Deficiency
Good Math
Scores Total
117
a b
dc
2 x 2 Table
Pollution Linked with Birth Defects in US Study
Total
118
a b
dc
2 x 2 Table
Pollution Linked with Birth Defects in US Study
Pollution
Birth Defects
No Pollution
No Birth
Defects Total
119
a b
dc
People who are not exposed
dc
2 x 2 Table
Pollution Linked with Birth Defects in US Study
Pollution
Birth Defects
No Pollution
No Birth
Defects Total
120
a b
dc
2 x 2 Table
Depressed Teens More Likely to Smoke
Total
121
a b
dc
People who do not have the outcome
d
b
2 x 2 Table
Depressed Teens More Likely to Smoke
Depression
Smoke
No Depression
No Smoke Total
122
a b
dc
2 x 2 Table
Smoking Linked to Youth Eating Disorders
Total
123
a b
dc
2 x 2 Table
Smoking Linked to Youth Eating Disorders
Smoke
Eating Disorders
No Smoke
No Eating
Disorders Total
124
a b
dc
People who are exposed and do not have the outcome
b
2 x 2 Table
Smoking Linked to Youth Eating Disorders
Smoke
Eating Disorders
No Smoke
No Eating
Disorders Total
125
a b
dc
2 x 2 Table
Total
Study Links Spanking to Aggression
126
a b
dc
People who have the outcome
a
c
2 x 2 Table
Study Links Spanking to Aggression
Spanking
Aggression
No Spanking
TotalNo
Aggression
127
a b
dc
2 x 2 Table
Total
Snacks Key to Kids’ TV-Linked Obesity – China Study
128
a b
dc
2 x 2 Table
Snacks Key to Kids’ TV-Linked Obesity – China Study
Snacks
Obesity
No Snacks
No Obesity Total
People who are not exposed and have the outcome
c
129
130
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
131
Laboratory
Teach Epidemiology
Making Group Comparisons and Identifying Associations
132
Laboratory
Teach Epidemiology
Making Group Comparisons and Identifying Associations
133
Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an
outcome.
Natural Experiment
Teach Epidemiology
Making Group Comparisons and Identifying Associations
134
An epidemiologic study of a natural experiment in which the investigator is not involved in the intervention other than to record, classify, count,
and statistically analyze results.
Observational Study
Teach Epidemiology
Making Group Comparisons and Identifying Associations
135
An epidemiologic experiment in which subjects are assigned into groups to receive or not receive
a hypothesized beneficial intervention.
Controlled Trial
Teach Epidemiology
Making Group Comparisons and Identifying Associations
136
Buprenorphine
Buprenorphine will stop heroin addicts from using heroin.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
137
Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an
outcome.
Observational Study of a Natural Experiment
Epidemiologic studies of natural experiments in which the investigator is not involved in the
intervention other than to record, classify, count, and statistically analyze results.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Laboratory
Teach Epidemiology
Making Group Comparisons and Identifying Associations
139
Making Group Comparisons and Identifying Associations
Teach Epidemiology
140
Making Group Comparisons and Identifying Associations
Teach Epidemiology
141
Stephen Jay Gould (survivor of abdominal mesothelioma)
Absolutely nothing in the available arsenal of anti-emetics worked at all. I was miserable and came to dread the frequent treatments with an almost perverse intensity. I had heard that marijuana often worked well against nausea. I was reluctant to try it because I had never smoked any substance habitually (and didn’t even know how to inhale). Moreover, I had tried marijuana twice (in the 1960s) … and had hated it …. Marijuana worked like a charm …. The sheer bliss of not experiencing nausea - and not having to fear it for all the days intervening between treatments - was the greatest boost I received in all my year of treatment, and surely the most important effect upon my eventual cure.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
142
A particular or detached incident or fact of an interesting nature; a biographical incident or
fragment; a single passage of private life.
Anecdote
Making Group Comparisons and Identifying Associations
Teach Epidemiology
143
Science
Transforming Anecdote to Science
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Anecdote
144
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cohort Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Case-Control Study
-
DZ
DZ
E
E
E
E
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Cross-Sectional Study
-
E
E
DZ
DZ
Making Group Comparisons and Identifying Associations
Teach Epidemiology
145
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cohort Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Case-Control Study
-
DZ
DZ
E
E
E
E
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Cross-Sectional Study
-
E
E
DZ
DZ
d
b
c
a
Making Group Comparisons and Identifying Associations
Teach Epidemiology
The goal of every epidemiological study is to harvest valid and precise information about the
relationship between an exposure and a disease in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public HealthAnn Aschengrau and George R. Seage III
Making Group Comparisons and Identifying Associations
Teach Epidemiology
147
Time Check
11:30 AM
148
149Teach Epidemiology
Teach Epidemiology
150
Time Check
12:30 PM
151
152Teach Epidemiology
Teach Epidemiology
153
The Journey
The Journey
Detectives in the Classroom - Investigation 2-6: The Journey
Analogy
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Study Design Epi Talk
Procedures and methods, established beforehand, that are followed by the investigator conducting the study.
Detectives in the Classroom - Investigation 2-6: The Journey
Timing
When are the passengers identified as exposed or unexposed?
E
When are the passengers identified as sick or not sick?
DZ
Timing
When does the epidemiologist start to observe the journey?
-
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E DZ
Label the Train Tracks
-
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Study Design:
E DZ
Label the Train Tracks
-
Controlled Trial
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Controlled
Trial
Flow Diagram
Flow Diagram
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Study Design:
Label the Train Tracks
Cohort Study
Detectives in the Classroom - Investigation 2-6: The Journey
Cohort Study
Just as in the controlled trial, the epidemiologist is also on the train during the entire journey. But there is an important difference. The epidemiologist is not telling passengers what to do. Rather, the epidemiologist is just observing them and counting. Passengers are not being told to have or not have an exposure, they are just living their normal lives. The epidemiologist, on the ride for the whole journey, just keeps observing everyone’s exposures and whether or not they develop the disease during the journey.
Label the Train Tracks
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E DZ
Label the Train Tracks
-
Study Design: Cohort Study
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Cohort
Study
Flow Diagram
Flow Diagram
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Cohort
Study
Flow Diagram
Flow Diagram
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Controlled
Trial
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Cohort
Study
Flow Diagram
Flow Diagram
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Controlled
Trial
Random Assignment
Detectives in the Classroom - Investigation 2-6: The Journey
Review
Observational StudiesEpi Talk
Epidemiologic studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results.
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Label the Train Tracks
Study Design: Case-Control Study
Detectives in the Classroom - Investigation 2-6: The Journey
The epidemiologist is not on the journey. Rather, the epidemiologist is waiting at the train station at the end of the journey. As passengers get off the train, the epidemiologist selects sick passengers for the case group and selects passengers who are similar but not sick for the control group. The epidemiologist then asks each person in the case group and control group questions about their exposures during the train ride. The epidemiologist relies on passengers’ memories of their exposures that occurred during the train ride.
Label the Train Tracks
Case-Control Study
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E
DZ
Label the Train Tracks
-
Study Design: Case-Control Study
Detectives in the Classroom - Investigation 2-6: The Journey
Case-Control
Study
Observational
Study
Flow Diagram
Flow Diagram
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
DZ
-
DZ
E
E
E
E
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Label the Train Tracks
Study Design: Cross-Sectional Study
Detectives in the Classroom - Investigation 2-6: The Journey
The epidemiologist, who has not been on the journey, stops the train somewhere during the trip (kind of like a train robbery) and takes a “snapshot” of all the passengers by asking them whether or not they have the exposure and whether or not they have the disease. Then the epidemiologist leaves the train and goes home to analyze the data from that particular day. The journey continues without the epidemiologist.
Label the Train Tracks
Cross-Sectional Study
Detectives in the Classroom - Investigation 2-6: The Journey
EDZ
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Label the Train Tracks
-
Study Design: Cross-Sectional Study
Detectives in the Classroom - Investigation 2-6: The Journey
Cross-Sectional
Study
Observational
Study
Flow Diagram
Flow Diagram
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E
E
-
DZ
DZ
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Controlled TrialEpi Talk
An epidemiologic experiment in which subjects are assigned into groups to receive or not receive a hypothesized beneficial intervention.
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Cohort StudyEpi Talk
An analytical epidemiological study design in which the investigator selects a group of exposed individuals and a group of unexposed individuals and follows both groups to compare the frequency with which the disease occurs in each group.
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Case-Control StudyEpi Talk
An analytical epidemiological study design in which the investigator selects a group of individuals with a disease (cases) and a group of similar individuals without the disease (controls) and compares the frequency with which an exposure occurred in the cases versus the controls.
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Cross-Sectional StudyEpi Talk
An analytical epidemiological study design in which the investigator selects a group of individuals and determines the presence or absence of a disease and the presence or absence of an exposure at the same time.
Detectives in the Classroom - Investigation 2-6: The Journey
180
181
182
Healthy People
-
Healthy People
E
E
O
O
O
O
Cohort Study
183
Handouts
184
185http://www.nationalchildrensstudy.gov/Pages/default.aspx
186
187
188
Science
Transforming Anecdote to Science
Making Group Comparisons and Identifying Associations
Anecdote
189
190
Healthy People
Flow Diagram
Randomized Controlled Trial
-
Healthy People
E
Random Assignment
E
O
O
O
O
191
Healthy People
Flow Diagram
-
Healthy People
E
E
O
O
O
O
Cohort Study
Observational
Study
192
http://abcnews.go.com/US/mystery-illness-hits-22-students-houston-texas-high/story?id=14888448#.Traba3Ltl8N
Handouts
193
Case-Control Study
O
-
O
E
E
E
E
194
http://www.youtube.com/watch?v=Xjgu2gYs2UQ
195
http://abcnews.go.com/US/mystery-illness-hits-22-students-houston-texas-high/story?id=14888448#.Traba3Ltl8N
Check Notes
196
197
Teacher Note: Enduring Epidemiological Understandings for the Epidemiology and the Energy Balance Equation Curriculum
1. Health and disease are not distributed haphazardly in a
population. There are patterns to their occurrence that can be identified through surveillance. Analysis of the patterns of health and disease distribution can provide clues for formulating hypotheses about their possible causes.
2. Causal hypotheses can be tested by conducting investigations of the exposures and outcomes of selected groups of people as they go about their lives. Information from these observational studies can be used to determine if an exposure and an outcome are associated. Because observational studies are complicated by factors not controlled by the observer, other explanations also must be considered.
198
Teacher Note: Authentic Assessment for Module 2 of the Epidemiology and the Energy Balance Equation Curriculum
199
Students will conduct, analyze, and interpret observational, cross-sectional studies among students in their class and then among students outside their class. Working in teams, students will have the opportunity to demonstrate their abilities to select a reasonable hypothesis of interest to them, design study questions about exposure and outcome, obtain informed consent, collect and manage data, calculate and compare prevalence rates, make accurate statements about whether their data support that hypothesis, and consider alternate explanations for what they observed. Reporting of results will be required, such as a written report, an item for the school newspaper, or an oral presentation or poster for students, teachers, and/or parents. Specific performance criteria will be used to help ensure that the experiences allow a genuine, realistic, and fair assessment of students’ comprehension of the Module 2 Enduring Epidemiological Understanding.
200
Teacher Note: Photos of Worksheets for Lesson 2-3
2-3b2-3a 2-3c
2-3d
Start of Lesson 2-3
(estimate 2 class periods)
201
202
Big Ideas in Lesson 2-2
• The cross-sectional design is an observational study of a natural experiment
• This design is relatively quick and simple, asking individuals about exposure and outcome at one point in time
• After the prevalence is calculated for the group with the exposure, the next question is “compared to what?”
• The “compared to what” consists of prevalence for the unexposed “controls”
• Dividing one prevalence by the other produces the prevalence ratio; it tells us if/how the exposure and outcome are associated
• Because exposure and outcome are measured at the same point in time, it is usually not possible to determine the time order of the exposure and the outcome (which came first) and as such, the association may not be interpretable
Review
Overview of Lesson 2-3
203
2-3a
Checklist - Study Planning Components and Expectations
2-3Study Hypothesis - Statement of a hypothesized association between an exposure and an outcome
2-3Study Variables - Developing questions about exposure and outcome , and additional questions about participants
2-3Questionnaire - Preparing a one-page sheet that study participants will fill out (typed and copies made)
2-4Draft Informed Consent Script - Preparing a script to be read to possible study participants (typed and copies made)
2-5 Plans for Study Conduct – Having assignments for study day
204
Notebook
Study
Part of 2-3aExpectations for Successful Completion
of Activities in Lesson 2-3
205
Notebook
Study
# Study Plan Component MetSome-what Met
Not Met
2-3Study Hypothesis - Statement of a hypothesized association between an exposure and an outcome1) Stated clearly; 2) makes sense at face value; and 3) is feasible to study in a school setting
□ □ □
2-3Study Variables - Developing questions about exposure and outcome 1) Clear questions that will mean the same thing to anyone who reads it; 2) a good description of what you are trying to measure; 3) a good understanding of challenges in measurement; and 4) an awareness of other information about study participants that will help in understanding study results
2-3
Questionnaire - Preparing a one-page sheet that study participants will fill out (typed and copies made)
Format of the survey that is user-friendly and clear in presenting questions and answer options and instructions
206
An educated guess
An unproven idea, based on observation or reasoning, that can be supported or refuted through investigation
A tentative explanation
Hypotheses
Hypotheses?
207
Hypotheses?
208
209
Tips
• Your hypothesis statement should state the hypothesized relationship between an exposure variable and an outcome variable, including the direction expected.
• Make sure that the hypothesis you choose is of genuine interest to you, because you will be spending your time and energy exploring it.
• Your stated hypothesis MUST NOT require the collection of any information that might be considered embarrassing, sensitive, or illegal.
• The hypothesis needs to be related to nutrition and/or physical activity.
• Eat school cafeteria food
• Regularly watch TV
• Have a sedentary lifestyle
• Have a high-fat diet
• Take multivitamins
• Eat breakfast
• Have perception of overweight
• Have good academic performance
• Regularly play computer games
• Eat junk food every day
Examples of Variables to Use in a Hypothesis
• Have a low-fat diet
• Regularly exercise
• Participate in a team sport
• Eat fruits and vegetables
• Drink high calorie drinks
• Drink diet soda
• Walk to school
• Get a good night’s rest
• Other ? ? ?
210
Some variables can be an exposure or an outcome
When is “eating more fruits and vegetables” an exposure?When is “eating more fruits and vegetables” an outcome?
Examples of Hypotheses:- People who eat more fruits and vegetables take more multivitamins - People who rarely watch TV are more likely to eat fruits and vegetables
When is “having more physical activity” an exposure?When is “having more physical activity” an outcome?
Examples of Hypotheses: - Physical activity is associated with a longer night’s sleep - People with high academic performance are more likely to also have more physical activity
211
212
2-3b Notebook
Study
Study Hypothesis
Why is your study team interested in testing this hypothesis?
Discuss the reason(s) your team thinks it will be possible to test this hypothesis in your class and school.
“X is associated with Y”
“People with X are more likely to have Y”
“People with X have higher, or more Y”
How do I state a hypothesis?
• Eat school cafeteria food
• Regularly watch TV
• Have a sedentary lifestyle
• Have a high-fat diet
• Take multivitamins
• Eat breakfast
• Have perception of overweight
• Have good academic performance
• Regularly play computer games
• Eat junk food every day
• Have a low-fat diet
• Regularly exercise
• Participate in a team sport
• Eat fruits and vegetables
• Drink high calorie drinks
• Drink diet soda
• Walk to school
• Get a good night’s rest
• Other ? ? ?
213
2-3b Notebook
Study
Study Hypothesis
A few examples of hypotheses to test
• Students who drink caffeinated drinks do more homework after school.• Students who drink caffeinated drinks get less sleep.• Healthy eating (at least 2 servings of fruit and vegetables a day) results in
better grades (“doing well in school.• Students that regularly eat vegetables have fewer periods of illness (24
hours or more of flu/cold symptoms). • Students who eat breakfast have fewer colds and therefore have fewer
absences from school.• A healthy breakfast is associated with playing in an organized sport. • Students who eat dinner with their family more often get better grades.• Students who skip lunch will eat more snacks.• People who eat more fruits and vegetables take more multivitamins.• Drinking more water is associated with eating more fruits and vegetables.• Students who drink more sweetened drinks are more likely to eat unhealthy
snacks.• Drinking at least 2 cans or a 20 ounce bottle of non-diet soda per day leads
to a crash (feeling tired). 214
OPTIONAL SLIDE TO SHOW STUDENTS
• Students who have one or more cats or dogs are more physically active.• Students who have one or more cats or dogs have more school absences
due to colds.• Receiving a daily, weekly, or monthly allowance is related to eating junk
food/unhealthy food more than twice a day.• Students who chew gum eat fewer snacks.• Students who listen to an IPOD are more likely to participate in physical
activity.• Students who text more are less physically active.• Watching more TV is associated with having lower stress levels.• Students who watch TV eat more snacks.• Students who regularly play video games eat more snacks.• Students who play regular video games (not active) eat more junk food.• Playing active video games is related to getting better grades.• Student athletes, on average, get more sleep than students who do not
participate in a sport.
215
OPTIONAL SLIDE TO SHOW STUDENTS
A few examples of hypotheses to test
• Students who participate in sports are more satisfied with their lives• Physical activity is associated with eating less junk food.• People who participate in a team sport are more likely to eat fruits and
vegetables.• Physically active students place greater weight on the importance of a
healthy lifestyle.• Regular exercise is related to higher academic performance.• Students who get 8 or more hours of sleep on average have higher
academic performance.• Students who sleep <8 hours a night eat more often than those who get at
least 8 hours of sleep.• Students who have less parental supervision are more likely to watch TV.• Students who have less parental supervision eat more junk food for after
school snacks.• High academic performance is associated with more physical activity.• High academic performance is associated with a healthy diet.
216
OPTIONAL SLIDE TO SHOW STUDENTS
A few examples of hypotheses to test
217
Possible break point between class periods
More Information about CHIS Study
Theresa A. Hastert, Susan H. Babey. School lunch source and adolescent dietary behavior. Prevention of Chronic Diseases 2009, Vol 6 (4).
http://www.cdc.gov/pcd/issues/2009/oct/08_0182.htm
218
Review: “Criteria for a Good Question”
• It should be clear and unambiguous, written so that its intended audience understands it.
• It should mean the same thing to everyone who reads it.
• The answer options must categorize and cover the entire range of possible behavior (from complete absence of the behavior to a maximum amount of the behavior).
• The time period to consider when answering a particular question must be appropriate (long or short enough) to capture the frequency of behavior desired (depending on the information desired and the type of behavior).
219
220
Exposure Question
During the school year, about how many times a week do you usually bring your own lunch to school from home?
012345
221
Outcome QuestionsTOPIC QUESTION
Fruit ?
Vegetables ?
Fast food ?
Soda ?
Fried potatoes ?
High-sugar foods ?
222
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables ?
Fast food ?
Soda ?
Fried potatoes ?
High-sugar foods ?
Outcome Questions
223
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food ?
Soda ?
Fried potatoes ?
High-sugar foods ?
Outcome Questions
224
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda ?
Fried potatoes ?
High-sugar foods ?
Outcome Questions
225
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda Yesterday, how many glasses or cans of soda, such as Coke, or other sweetened drinks, such as fruit punch or Sunny Delight did you drink? Do not count diet drinks.
Fried potatoes ?
High-sugar foods ?
Outcome Questions
226
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda Yesterday, how many glasses or cans of soda, such as Coke, or other sweetened drinks, such as fruit punch or Sunny Delight did you drink? Do not count diet drinks.
Fried potatoes Yesterday, how many servings of French fries, home fries, or hash browns did you eat?
High-sugar foods ?
Outcome Questions
227
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda Yesterday, how many glasses or cans of soda, such as Coke, or other sweetened drinks, such as fruit punch or Sunny Delight did you drink? Do not count diet drinks.
Fried potatoes Yesterday, how many servings of French fries, home fries, or hash browns did you eat?
High-sugar foods Yesterday, how many servings of high-sugar foods, such as cookies, candy, doughnuts, pastries, cake or popsicles did you eat?
Outcome Questions
Questions for your Cross-Sectional Studies
• One question must obtain information about the
exposure in your hypothesis and the other question must obtain information about the outcome in your hypothesis.
• The study information on exposure and outcome must fit into a 2x2 table.
• A “yes/no” question will fit and is recommended.
• If using a multiple choice question, you will need a predetermined “cut point” so there is a “higher/lower” range to fit into the 2x2 table.
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Yes Exposure
Total
No Exposure
a b
c d
Yes Outcome
No Outcome
The 2x2 table
Exposure and Outcome
Distributions Among Individuals in a Study Population
Optional: Use as needed for
review of 2x2 tables and
necessity for a question about
exposure and a question about
outcome
229
2-3c
Study Variables: Questions About Exposure and Outcome and
Additional Questions
230
Notebook
Study
How should we ask
about eating a healthy
breakfast?
“Criteria for a Good Question”
• It should be clear and unambiguous, written so that its intended audience understands it.
• It should mean the same thing to everyone who reads it.
• The answer options must categorize and cover the entire range of possible behavior (from complete absence of the behavior to a maximum amount of the behavior).
• The time period to consider when answering a particular question must be appropriate (long or short enough) to capture the frequency of behavior desired (depending on the information desired and the type of behavior).
231
2-3c
Item 5 - Labeling a 2x2 Table
232
Notebook
Study
2x2 Table Fill in the two boxes in the table below, to show how your exposure and outcome variables will be analyzed in a contingency table in order to test your hypothesis. (Note: if you plan to use multiple choice questions for your exposure and/or outcome, determine cut points for the data so that you can fill in the contingency table below.)
233
2-3c
Item 6 – Additional Questions Notebook
Study
Think about what other information about students in your study would be interesting to know, in terms of your hypothesis. (Hint: perhaps gender would be one of these)
In the space below, write any additional questions for your questionnaire that will gather information about these other characteristics of your study subjects. .
Should we ask about gender?
Questions to Gather Additional Information on
Participants
Break Between Classes
234
235
2-3d
Sample Questionnaire for for Cross-Sectional Study
Notebook
Study
Thank you for your participation in this survey. Please answer the questions below by circling one choice for each question. When you are finished, fold this paper in half and follow instructions for handing in your questionnaire.
Remember: Do not write your name anywhere on this paper.
Study Questions: (Circle one answer for each question) 1. During the past month, did you usually eat 2 or more servings of fruits/vegetables per day? Yes No 2. In the last semester that you have completed, did you have a grade average of A or B? Yes No
3. What is your gender? Male Female 4. What grade are you in? 6th grade 7th grade 8th grade
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Type your questionnaire
Make enough copies for all
potential study
participants
237
Big Ideas in Lesson 2-3
• A good study plan includes careful thought about choice of exposure and outcome variables and high-quality questions to measure them
• Additional questions about other characteristics of participants can be asked in order to better understand study results
• A well-planned study has a user-friendly questionnaire to administer to participants
Re-Cap
238
Time Check
2:15 PM
239
240Teach Epidemiology
Teach Epidemiology
Teach Epidemiology
Teachers Team-Teaching Teachers (TTTT)
News Item
Team leads other workshop participants in the analysis of a news item from an
epidemiological perspective.
1
Teach Epidemiology
Teachers Team-Teaching Teachers (TTTT)
News Item
Team leads other workshop participants in the analysis of a news item from an
epidemiological perspective.
2
Teach Epidemiology
Teachers Team-Teaching Teachers (TTTT)
Existing Lesson
Team leads other workshop participants in a portion of a selected existing epidemiological lesson.
3
Teach Epidemiology
Teachers Team-Teaching Teachers (TTTT)
Existing Lesson
Team leads other workshop participants in a portion of a selected existing epidemiological lesson.
4
TTTT Rules
245
1. Teach epidemiology
2. As a group, create a 30-minute lesson during which we will develop a deeper understanding of an enduring epidemiological understanding.
3. Focus on the portion of the unit that is assigned. Use that portion of the unit as the starting point for creating your 30-minute lesson.
4. When teaching assume the foundational epidemiological knowledge from the preceding days of the workshop.
5. Try to get us to uncover the enduring epidemiological understanding. Try to only tell us something when absolutely necessary.
6. End each lesson by placing it in the context of the appropriate enduring epidemiological understanding.
7. Teach epidemiology.
8. After the lesson, metacognitate about your preparation for and teaching of the lesson.
Teach Epidemiology
246
They can then use that ability to think about their own thinking … to grasp how other people might learn. They know what has to come first,
and they can distinguish between foundational concepts and
elaborations or illustrations of those ideas.
They realize where people are likely to face difficulties developing their own comprehension,
and they can use that understanding to simplify
and clarify complex topics for others, tell the right story, or raise a powerfully provocative question.
Ken Bain, What the Best College Teachers Do
Metacognition
Teach Epidemiology
Teachers Team-Teaching Teachers (TTTT)
247
Time Check
2:45 PM
248
249Teach Epidemiology
Teach Epidemiology
250
Time Check
3:00 PM
251
252Teach Epidemiology
Teach Epidemiology
253
Broadcast Studios
Teach Epidemiology
Tours
254
Time Check
4:00 PM
