Project Overview• Identify our cases: Students in 2nd

period statistics• Identify the variable: heartbeat/heart

rate depending on music• Type of variable: quantitative• Type of sample taken: Stratified –

because it is a category 2nd period stats.

Statistics AMs. Sanchez

Trimester 1 – Week 2

Unit 2 – StudiesExperimental

vs. Observational

Experiment vs Observational Studies

• Observational Study: Observe individuals and collect data, measure variables. There is no outside influence, and we do not impose any treatment or solution to what is observed.

• Experiments: We deliberately impose some type of treatment on units and we observe their response.

Experimental vs Observational

Experimental Observational

• Using 100 healthy lab rats

• Assign 50 to be exposed to cigarette smoke treatment

• Assign other 50 to a non-smoking treatment

• After 6 months measure their lung capacity of both groups and compare results.

• Find 100 individuals

• 50 who have been smoking for the past 10 years

• 50 who have never smoked in their lifetime

• Measure their lung capacity and compare results.

Exercise #1• Determine if the following scenarios are examples of experimental or

observational studies.

1. Researchers surveyed a large sample of adults. For each adult they recorded whether the person had tried an illegal substance at any period of their life and whether or not it had affected them way.

2. Researchers believe that the presence of a floral scent could improve a person’s learning ability in certain situations they had 11 people work through a pencil and paper maze 6 times - 3 times while wearing a floral scented mask and 3 times wearing an unscented mask.

3. The CDW caught 41 bighorn sheep on Mt. Evan and gave them an injection to prevent heartworms. A year later 38 of those sheep did not have heartworm the other 3 did.

4. The CDW imposed special fishing regulations on the Decker’s section. All trout under 15 inches had to be released. A study found that before and after the regulation the average length of the trout was 4.2 inches

Experimental Design - Vocabulary

• Experimental Units: living organisms on which the experiment is done.

• Subjects: when the units are human beings

• Treatment: specific experimental condition applied to the units

• Placebo: dummy treatment

Experimental Design - Vocabulary

• Placebo Effect: occurs when a subject is made believe they have receive a treatment and they respond favorably.

• Control group: Groups that does NOT receive treatment.

• Treatment group: Group that DOES receive treatment.

Example – Identify the following

• Researchers used 100 healthy lab rats, they assigned 50 to be exposed to cigarette smoke treatment and the other 50 to a non-smoking treatment. After 6 months measure their lung capacity of both groups and compare results.

Subjects/Experimental Units: 100 lab ratsTreatment: Exposure to cigarette smoke vs non exposureControl Group: 50 rats who were NOT exposed to smokeTreatment group: 50 rats who were exposed to smoke

Exercise #2• Identify the treatment, subjects/units, control and treatment

groups of the following.1. Researchers designed an experiment to see if studying before

going to bed made you learn/memorize things better. 200 subjects were asked to study a few vocabulary words in another language with their definition, 100 were asked to study them right before bed and the other 100 were asked to study them at any time during the day. The following day both groups were tested.

a. Subjects/Unitsb. Treatmentc. Control Groupd. Treatment Group

2. Scientist want to test the effects of a new experimental drug. They gather a group of 100 rats, 50 are injected with the drug for the next 2 weeks and the other 50 are not. After 3 weeks scientist compare health between the two groups.

3. Researchers want to determine the effect of anger management therapies. A group of 20 students is selected for the study, all 20 are exposed to a stressful situation. 10 are given a pillow to hit, the other group is left to wait for 5 minutes. After 5 minutes both groups are asked to fill out a survey.

Randomization for treatments

• Recall: Randomization helps eliminate bias and leaves the subjects/units up to the laws of probability making it easier for us or the researchers to analyze.

• It is difficult to account for all variables that might influence a subject’s response to a treatment. Sometimes subjects are assigned to a treatment or control group in a carefully matter – by age, gender, smoker etc. This is called Block Design

• However a more common way to assign patients to a treatment and control group is by using Randomization.

Example of Block Design

• Block Design: divide the population into similar subjects of large groups. Then assign subjects within each block to both treatments.

• The CDW is testing a new medicine to help with allergies, 100 subjects were selected for the research. They were divided by age groups. Some subjects were injected with the medicine and others were injected with a non invasive liquid (Placebo)

18-40

41 and older

Randomize

Randomize

Group 2: Injected with the placebo

Group 1: Injected with Medicine

Group 1: injected with medicine

Group 2: injected with the placebo

Compare Results

Compare Results

Prevent Allergies

Exercise #3• Create a block design for each of the following scenarios

1. Researchers believe that the presence of a floral scent could improve a person’s learning ability in certain situations they had 50 subjects, then divided them into groups by education background - finished HS only and finished college. Some were asked to wear a scented mask or others without a mask.

2. A statistical study is designed to test if classical music helps learn mathematics better. They gathered 100 subjects and divided them by gender. Subjects were asked to study the procedure to solve a mathematical problem, some were listening to classical music and others were not listening to anything.

Example of Random Design • Can chest pain be relieved by drilling holes in the

heart? - A hospital in New York City provided some information about this issue using a randomize two treatment experiment. A group of 298 volunteers with severe untreatable chest pain were randomly assigned to get the laser or not. The Random design can be picture as follow:

Patients with chest pain

Random assignments

Group 1 149 patients

Group 2 149 patients

Treatment 1Laser holes in heartTreatment 2No laser holes in hear (Placebo)

Compare pain relief

Exercise #4• Create a random experimental design for each of the following

scenarios.

1. Researchers designed an experiment to see if studying before going to bed made you learn/memorize things better. 300 subjects were asked to study a few vocabulary words in another language with their definition. Their treatments are making them study before going to bed or studying at any time during the day. The next day they take a test over the vocabulary.

2. Scientist want to test the effects of a new experimental drug. They gather a group of 400 rats. The treatments are injecting the rats or not injecting them. After 2 weeks we compare health conditions between the two groups.

3. Researchers want to determine the effect of anger management therapies. A group of 80 students are selected for the study, the two treatments are hitting a pillow or left to wait 5 minutes. After 5 minutes both groups are asked to answer a survey.

Blind Experiments• Scenario: Let’s say you’re participating in an

experiment to determine if drinking a sport drink makes you more energetic versus drinking water.

• If you drink the energy drink – you may subconsciously or consciously try to act more energetic this is Participation Bias.

• Sometimes we also experience Experimenter’s Bias, in which the researchers implements, collects or analyzes the data in a biased manner to favor the outcomes of the study.

• To avoid these researchers use Blind Experiments.

Single Blind vs Double Blind Experiments• Single Blind Experiment: researchers

know who is getting what treatment but the subjects do not. This is to avoid participation bias.

• Double Blind Experiment: both the subjects and the researchers do not know who is getting which treatment. This is to avoid participation bias AND experimenter’s bias.

Exercise #5Identify the following as single or double blind experiments.

1. Researchers are implementing a clinical trial for 3 new drugs with human subjects. The researchers and the subjects do not know who is getting/receiving which treatment.

2. In a study regarding the effects of a new headache medicine. Researchers give out the new medicine and a sugar pill. In this case the subject are told they are receiving the new medicine.

3. Researchers are testing a new kind of painkiller. They have 90 volunteers, 30 get the new medicine, 30 the old, and 30 a placebo. The researchers handling the medicine or placebo do not know which subjects are getting which pill and neither do the subject.

Surveys• Most common way to gather data about people.

Ask questions, about opinions.• They can be as simple as a: Yes or No answers• To a rating: of agree to disagree, something you

like or dislike, etc.

Survey Responses

• Voluntary Response: often represent people with strong opinions – mostly bias, since these types of responses are from people who seek surveys to fill out.

• Nonresponse: when the selected respondent cannot be contacted or refuses to respond (happens most in Census)

Types of Bias in Surveys

• Statement Bias: whenever a survey provides a statement that is trying to persuade you to incline a certain way.

EX.1. The 2nd Amendment in the bill of rights says that

we have the right to bear arms. What are your thoughts on gun regulation?

2. Most religions believe that all lives are sacred. What is your position regarding abortion rights?

Types of Bias in Surveys

• Interviewers Bias: whenever the interviewer, consciously or unconsciously, tries to persuade you to answer in a certain way. Maybe with a verbal statement, something they are wearing, or the social status that person holds.

Types of Bias in Surveys

• Anonymity: Sometimes whenever a survey is asking sensible questions your response might change if you feel that your name is going to be attached to that response versus the answer you’ll give if you are answering anonymously.

Exercise #6• Categorize the following as, statement, interviewer's, or

anonymous bias. AND STATE WHY

1. Teachers are taking a poll to see who is the best teacher in the school. The question survey reads “Write down the name of the best teacher(s) you’ve had during your HS education”

2. A school is taking a poll regarding drug use in the school. The survey reads: “Have you or any one you know used illegal drugs on campus”, at the end of the page it ask for the students name and grade year.

3. A political survey is taking a poll regarding the popularity of certain candidate. The survey question reads: “The candidate has been in office for 2 years, they have done great things for the community. Are you going to give them your vote in this coming election?”

INTERACTIVE QUIZ• There are 6 stations – regarding the 6 new

vocabulary and activities we have been working on during this week.

• Instructions: You will work in teams of 3 – 4 each of you will answer the quiz but I will only grade one of them that will be the grade for all of you. You are allowed to use your notes, to answer the quiz.

• Each station has different questions, REMEMBER I will pick one paper at random and that will be the grade for the entire group therefore WORK IN TEAMS AND COMMUNICATE YOUR ANSWERS!