1. Do Now- Identify the sampling method (Cluster or stratified)
Instructors teaching research methods are interested in knowing what study techniques their students are utilizing. Rather than assessing all students, the researchers randomly select 10 students from each of the sections to comprise their sample.
Instructors teaching research methods are interested in knowing what study techniques their students are utilizing. Rather than assessing all students, the researchers randomly select 2 sections and research all the students in those 2 sections to comprise their sample.

2. Observational Studies vs. Experiments
Lesson 4.2 Day 1
Observational Studies vs. Experiments

3. Objectives
Explain the concept of confounding and how it limits the ability to make cause-and-effect conclusions.
Distinguish between an observational study and an experiment, and identify the explanatory and response variables in each type of study.
Identify the experimental units and treatments in an experiment.

4. Complete #1-5 with your groups

5. Debrief

6. #5
Randomly choose 100 juniors to be a part of the experiment. Randomly split them up so half of them take the class and the others don’t. After the course is over all juniors take the SAT. We compare the average scores of the groups.

7. Definitions
Observational studies: no treatments imposed, we only observe
Experiments: treatments imposed, allows for causation

8. Definitions Explanatory Variable: used to predict
More than 1 are called factors
Factors have levels
Response variable: outcomes

9. Definitions Treatment: what is done to participants
Experimental Units: what/who the treatment is imposed on
Confounding variables: variables not controlled for that affect results

10. Random sample vs random assignment
Random Sample: A random sample should be representative of the population from which it was taken, so a random sample allows us to generalize our conclusion to the population.
In the SAT prep class example, we have 44 student volunteers.  Thus we cannot generalize our conclusion to all students.  Instead we can only make a conclusion for these 44 students or other students like the ones who volunteered for the experiment.

11. Random sample vs random assignment
Random Assignment: Random assignment hopefully will equally distribute the various levels of the confounding variables into the treatment groups, so that only difference between groups is the treatment.  If there is a significant difference between the groups, the random assignment allows us to conclude that the treatment caused the difference.

12. Check your understanding
Do Now: Complete check your understanding from yesterday’s worksheet

13. Designing Experiments
Lesson 4.2 Day 2
Designing Experiments

14. Objectives
Describe the placebo effect and the purpose of blinding in an experiment.
Describe how to randomly assign treatments in an experiment using slips of paper, technology, or a table of random digits.
Explain the purpose of comparison, random assignment, control, and replication in an experiment.

15. Would you fall for that?
Video

16. #2 There is nothing to compare to. → Control Group
Sugar might increase pulse rate. → Control other variables
People know they’re getting caffeine so it could be placebo effect. →Blinding

17. Design an experiment
Take the students and randomly split them into 2 groups. Give one group regular coke and the other caffeine-free. Compare their change in heart rate.
Create a diagram for this experiment.

18. Do Now
What are the effects of repeated exposure to an advertising message? The answer may depend on both the length of the ad and on how often it is repeated. An experiment investigated this question using 120 undergraduate students who volunteered to participate. All subjects viewed a 40-minute television program that included ads for a digital camera. Some subjects saw a 30-second commercial; others, a 90-second version. The same commercial was shown either 1, 3, or 5 times during the program. After viewing, all the subjects answered questions about their recall of the ad, their attitude toward the camera, and their intention to purchase it.
A) For the advertising study, identify the experimental units or subjects, explanatory and response variables, and the treatments.

19. Definitions
Control Group: used to provide baseline data for comparison.
Blinding: When subjects (single-blind) and/or experimenters (double-blind) who interact with subjects are unaware of what treatment was assigned.
Placebo Effect: When a fake treatment works.

20. Double-Blind: there should be another researcher who would know who received what treatment.  However, even if there was not, the researcher could cover the pill bottles and mix them up.  Then they could dispense treatment and uncover the bottles later to see which group had each treatment.

21. 4 key principles of experiments
Comparison - 2 or more treatments
Random Assignment – use a chance process to assign treatments to experimental units
Control - keep all other variables besides treatments constant
Replication: using enough experimental units to distinguish differences.

22. Do Now
Complete #1a and d on check your understanding on lesson 4.2 day 2 worksheet

23. Some more ideas to note…
The Language of Experiments
Suppose that we thought that the temperature of the Coca Cola might also effect the pulse rate.  So not only are we using Coke and Caffeine Free Coke, we are also testing it at 35 degrees, 50 degrees, and 70 degrees.
Factor: A variable that is manipulated and may cause a change in the response variable (presence of caffeine and temperature).
Levels: The different values of the factors.  The factor “presence of caffeine” has two levels (yes and no) and the factor “temperature” has three levels (35, 50, and 70 degrees).
Treatments: A specific condition applied to the individuals in an experiment.  In this experiment, there are 6 treatments: (Yes, 35), (No, 35),  (Yes, 50), (No, 50), (Yes, 70), (No, 70).

24. Do Now
What are the effects of repeated exposure to an advertising message? The answer may depend on both the length of the ad and on how often it is repeated. An experiment investigated this question using 120 undergraduate students who volunteered to participate. All subjects viewed a 40-minute television program that included ads for a digital camera. Some subjects saw a 30-second commercial; others, a 90-second version. The same commercial was shown either 1, 3, or 5 times during the program. After viewing, all the subjects answered questions about their recall of the ad, their attitude toward the camera, and their intention to purchase it.
A) For the advertising study, identify the experimental units or subjects, explanatory and response variables, and the treatments.
B) Identify the number of factors and amount of levels each factor has.

25. Check your understanding

26. Randomized Block Design
Lesson 4.2 Day 3
Randomized Block Design

27. objectives Describe a completely randomized design for an experiment.
Describe a randomized block design and a matched pairs design for an experiment and explain the purpose of blocking in an experiment.

28. Complete #1 with your group

29. Complete #2 with your group
Complete #2 with your group. Put your diagram/outline on the provided whiteboard for me to check. Try your best!

30. Discuss #3 with your group and then we’ll discuss as a class.

31. Do Now
What are the effects of repeated exposure to an advertising message? The answer may depend on both the length of the ad and on how often it is repeated. An experiment investigated this question using 120 undergraduate students who volunteered to participate. All subjects viewed a 40-minute television program that included ads for a digital camera. Some subjects saw a 30-second commercial; others, a 90-second version. The same commercial was shown either 1, 3, or 5 times during the program. After viewing, all the subjects answered questions about their recall of the ad, their attitude toward the camera, and their intention to purchase it.
A) For the advertising study, identify the experimental units or subjects, explanatory and response variables, and the treatments.
B) Identify the number of factors and amount of levels each factor has.

32. #3 debrief
Notice that the matched pairs design is really just a fancy version of a block design, where each block is of size 2 (two students paired with similar GPAs).

33. Definitions
Block- group of experimental units that are known to be similar
Randomized Block Design – separate subjects into blocks and then randomly assign to treatments within each block

34. definitions
Matched pairs - experiment used to compare two treatments that uses blocks of size 2
Two very similar experimental units are paired and then randomly assigned to a treatment.

35. Which variable should be used for blocking? Why block?
Should we create blocks of Juniors and Seniors?  Blocks of males and females?  Blocks of high GPA and low GPA?
Which variable?  Choose the one that is most strongly associated with the response variable.  We think grade level is the variable that is most strongly associated with differences in SAT scores.
Why block? To reduce the variability in the response variable (SAT score).  The variability of SAT scores should be less in each block then it would be for the whole group.  This can help make it easier to determine if results are statistically significant (increase power).  

36. The thinking and reasoning here is very similar to making the choice of variable to use when doing a stratified random sample (like the choice of stratifying by row in the Justin Timberlake lesson).

37. Check your understanding

38. Are ELEPHANTS REALLY AFRAID OF MICE?

39. Answer the following on your whiteboard with your group
1) Identify the following:
experimental units
response variable
treatment
explanatory variables or factors
2) Was there a control group? Why?

40. Read the provided article
In your groups, read your assigned article and identify the:
experimental units
response variable
treatment
and factors from the study. 
Be prepared to summarize your article and share your answers with the class