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Unit 2 Research Methods: Thinking Critically with Psychological Science. I. The Need for Psychological Science. I. The Need for Psychological Science. A. Hindsight bias B. Overconfidence. 98% Certainty. The area of the US in square miles? The population of Australia 2007? - PowerPoint PPT Presentation
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98% Certainty
1. The area of the US in square miles?
2. The population of Australia 2007?
3. American battle deaths in Spanish-American War?
4. Female psychiatrists in the US in 2005?
5. Operating nuclear plants worldwide in 2007?
98% Certainty
1. Area of US:
2. Australian pop.:
3. Battle deaths:
4. Female psychiatrists:
5. Nuclear plants:
3.6 million sq. miles
20.4 million
385
13,079
435
I. The Need for Psychological Science
A. Hindsight biasB. OverconfidenceC. Scientific attitude 1. Curiosity 2. Skepticism 3. Humility 4. Critical thinking
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles a. Theories b. Hypotheses c. Operational definitions d. Replication
Theory• Explanation using a set of principles that
organizes observations and predicts behavior or events– Not just a guess– Based on research and tested information– Organize isolated facts = simplify
Ex. “Sleep improves memory”
Hypothesis
• Testable prediction implied by a theory– Not an “educated guess”– A testable question based on a theory– Has testable predictions
Ex. “When sleep deprived, people remember less from the day before.”
Operational Definition• Statement of the exact procedures (operations) used
in a research study– Leaves nothing to subjectivity– Explains specifically
Ex. “Sleep deprived = X hours or less”
Let’s practice – create an operational definitionn for the following:
HappinessPopularityGood musicIntelligence
Replication
• Repeating the study, usually with different participants to see if the finding extend to others– To be a valid finding, it must be replicable
Scientific Method
Theory
Hypothesis
Research &Observation
Confirm, Reject,Revise
Don’t forget your operational
definitions so it can be repeated
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies
Phineas Gage1823-1860
(1) Problem?Can be misleading
(2) Why used?Provides study opportunities
not otherwise available
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies b. Surveys (1) Wording effects
72% interested in “plants & trees”39% interested in “botany”
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies b. Surveys (1) Wording effects (2) Sampling (a) Populations
All those in group being studied (b) Random samples
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques a. Case studies b. Surveys c. Naturalistic observation
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques 3. Correlation and prediction a. Types b. Scatterplots
II. Asking & Answering Questions3. Correlation and prediction b. Scatterplots c. Correlation coefficients (useful at .2 and up/higher numbers
= greater predictability
II. Asking & Answering Questions3. Correlation & prediction c. Correlation coefficients d. Correlation does not establish cause & effect!!!!!!!
There is a correlation between TV watching and GPA
What do we know about cause and effect?
II. Asking & Answering Questions3. Correlation & prediction d. Correlation does not establish cause & effect!!!!!!! e. Illusory correlation
o perception of a relationship where none existso Ex: Getting wet and chilled causes people to
“catch a cold”o Ex: Infertile couples are more likely to conceive
after they adopto Sometimes we forget, random coincidences are
really are just random – we deceive ourselves by seeing a connection that isn’t there
II. Asking & Answering Questions3. Correlation & prediction d. Correlation does not establish cause & effect!!!!!!! e. Illusory correlation f. Random may not seem random
II. Asking & Answering QuestionsA. The scientific method 1. Basic principles 2. Descriptive techniques 3. Correlation and prediction 4. Experimentation and causation
Experimentation
Purpose of an expt:
General hypothesis: food affects learning
Specific (operationalized) hypothesis: students who eat an oatmeal raisin cookie before class each day will have higher average scores on the semester final than students who don’t eat a cookie.
Eating cookies before class each day will lead to higher average scores.
Variables:Independent (IV)
Controlled by experimenterThe “cause” variable
Dependent (DV)Predicted by experimenterThe “effect” variable
Eating cookies before class each day will lead to higher average scores.
Groups (conditions): to establish different levels of the IV
Experimental groupExposed to IVGet cookie
Control groupNot exposed to IVNo cookie
What if kids get cookies and A’s?
Eating cookies before class each day will lead to higher average scores.
IV DV
Expt. Gp. Cookie 95%
Cntrl. Gp. No Cookie 82%
ConfoundingVariables
Environmental
Expectations
Individualdifferences
Random SamplingTo select participants from populationAllows you generalize results
Random AssignmentTo divide participants into groupsControls confounding variables
Eating cookies before class each day will lead to higher average scores.
IV DV
Expt. Gp. Cookie 95%
Cntrl. Gp. No Cookie 82%
85%
93%
Statistical Significance
p value
likelihood a result is caused by chance
can be no greater than 5%
p ≤ .05
Replication
Non-replicated results are preliminary.
Linus Pauling (1970). Vitamin C prevents colds.
IV DV
Expt. Gp. Vit C
Cntrl. Gp. Placebo
Expt. Gp.45%
Fewer colds
Experimental Design Terms
• Hypothesis• Operational definitions• Participant selection• IV & DV• Experimental & control groups• Confounding variables• Random assignment• Placebo control• Double blind procedure• Statistical significance (p value)• Replication
Practice with IV & DV
• Exposing children to public television improves their reading.
• You’ll have fewer problems in the future if you get psychotherapy.
• Getting complements makes people work harder on an assembly line.
Students are more likely to smile for their senior pictures if they have a friendly photographer.
IV?
DV?
III. Statistical Reasoning
A. Describing data
0. Frequency distributions
A 40 4 45%39 738 1037 836 15
B 35 8 32%34 833 832 7
C 31 4 16%30 529 728
D 27 5%26 225 124 2
F <24 1 1%
1. Bar graph (histogram) 2. Line graph (frequency polygon)
III. Statistical Reasoning
A. Describing data 0. Frequency distributions 1. Central tendency
43544
a. Mode --Most common=4 b. Mean --Arithmetic avg=20/5=4 c. Median --Middle score=4
Central Tendency 1968 TOPPS Baseball Cards
Nolan Ryan $1500
Billy Williams $8
Luis Aparicio $5
Harmon Killebrew $5
Orlando Cepeda $3.50
Maury Wills $3.50
Jim Bunning $3
Tony Conigliaro $3
Tony Oliva $3
Lou Pinella $3
Mickey Lolich $2.50
Elston Howard $2.25
Jim Bouton $2
Rocky Colavito $2
Boog Powell $2
Luis Tiant $2
Tim McCarver $1.75
Tug McGraw $1.75
Joe Torre $1.5
Rusty Staub$1.25
Curt Flood $1
With Ryan:Median=$2.50Mean=$74.14
Without Ryan:Median=$2.38Mean=$2.85
III. Statistical Reasoning
A. Describing data 0. Frequency distributions 1. Central tendency 2. Variation a. Range b. Standard deviation
Standard DeviationPunt
Distance
36384145
Mean=160/4=40 yds
Deviationfrom Mean
-4-2+1+5
DeviationSquared
16 4 125
46
46/4=11.5=variance
std. dev.=
variance=
11.5=3.4 yds
III. Statistical Reasoning
A. Describing data 0. Frequency distributions 1. Central tendency 2. Variation 3. The normal curve
III. Statistical Reasoning
A. Describing dataB. Making inferences 1. Can you generalize from sample to pop.? a. Is sample unbiased? Or is it a rep. sample? b. Is there low variability in sample? c. Is the sample large? More is better… 2. Is the diff. between two gps. stat. significant? a. Is the difference large? Is it reliable? b. Is there low variability within the groups? c. Is p ≤ .05?
VI. FAQs
A. Can lab expts illuminate real life?
B. How important are gender and culture?
C. Why study animals? Is it ethical?
D. Is it ethical to experiment on people?
E. How is psychology affected by values?
VI. FAQs
A. Can lab expts illuminate real life?– Focus is not on particular behavior, but on general
principles– Similar to using wind tunnel to build airplanes
VI. FAQs
B. How important are gender and culture?– Specific attitudes and behaviors can vary by
gender & culture, but underlying processes are often the same
– Kids everywhere like sports, but in the US you don’t usually find them playing barefoot in the street
– Men & women express/detect emotion differently, but both learn to walk about the same age
VI. FAQs
C. Why study animals? Is it ethical?– They have provided a cure for rabies,
understanding aging, relieving fears and depression
– Ethical… That is the debate and the answer varies by country and critter• Rats and sea slugs? Sure, but not puppies and
chimps…
VI. FAQs
D. Is it ethical to experiment on people? Yes, if the APA’s ethical guidelines are
followed.
1. Informed consent
2. Protection from harm
3. Confidentiality
4. Debriefing
VI. FAQs
E. How is psychology affected by values? – How and what we study• Worker productivity or worker morale?• Conformity or indepenence?
– How we describe things• Firm or stubborn?• Faith or fanaticism?
Assignments
• Must be word processed and printed out.• Must be ready by the beginning of the class
period.
How should participants be chosen?
• Good answers use and make clear your understanding of the terms “sample” and “population.”
• Good answers explain how to draw a random sample.
• Ex. “All the assembly line workers for a company could be the population. I would draw a random sample of 40 of them by picking names from a hat.”
Create operationalized hypothesis
• Good answers make an educated guess (“Workers who are complimented will work harder”)
• Good answers develop specific, measurable ways to define compliments and hard work.
• Ex. “10 compliments praising work effort will be given at four specific times.” “Supervisors will give compliments from a pre-developed list.” “Hard work will be measured by using the number of items produced each hour.”
Identify IV & DV
• IV=compliments• DV=work effort• Do not propose a direction when stating the
variable (“the DV is an increase in work.”)• People are never the variables (“the IV is the
people who get complimented.”)
Describe the groups
• Experimental group gets compliments.• Control group doesn’t get compliments.• Use the terms!
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