1. Internal Validity - The extent to which all explanations for changes in the DV between conditions have been eliminated -- other than the IV.
ie(7a)

2. Extraneous variable - any variable other than IV that effects DV.
Control
Experimental
Extraneous
Variable
ie(7a)

3. Control Confound Experimental
Confounding Extraneous Variable - any extraneous variable that affects one condition differently than it affects other conditions.
ie(7a)

4. Between Subjects Designs
Two (or more) Groups of Participants compared to each other. Each group has a different level of the IV.
Experimental (Treatment) Group
Control Group
ie(7a)

5. Major Potential Confound: Individual Differences (I. e
Major Potential Confound: Individual Differences (I.e., perhaps the participants in one group are not comparable in many ways to participants in the other group).
ie(7a)

6. Within Subjects Design
One Group of participants measured under more than one condition of the IV.
Experimental Condition
Control Condition
Potential Confounds
Since subjects cannot be in more than one condition at one time, anything that is not the same at each of the times of measurement (other than the IV) is a potential confound.
ie(7a)

7. Pre-Post Test Designs (type of WS design)
Pre-test - DV measured before Treatment
- serves as baseline control condition
Post-test - DV measured after Treatment
ie(7a)

8. Confounds with Pre-Post Designs
Other than the treatment (IV) what could cause difference in DV between conditions (I.e., what possible confounds could there be?)
Confounds with Pre-Post Designs
History - any changes that occurred between
Pre and Post Test other than IV.
ie(7a)

9. Maturation - biological/psychological changes between pre-post test.
ie(7a)

10. Instrumentation - changes in measurement device or operational definition between pre and post test.
ie(7a)

11. Attention Deficit Disorder?
Are rates of Diabetes really increasing, or are we simply diagnosing more cases???
Attention Deficit Disorder?
DUIs?
ie(7a)

12. Testing : Changes is a person’s score for the post conditions that results from having been tested in the pre-test.
Sensitization
Boredom
Practice
ie(7a)

13. Attrition - subjects dropping out of the study.
ANYTHING that is a difference between the
before and after condition other than the IV is
a confound.
ie(7a)

14. Hokey Pokey
ie(7a)

15. Artifact - Effect caused by the procedure rather than by the IV.
Statistical Regression Artifact.
- problem when subjects are assigned to groups
based on the pre-test scores.
- group scores will be pulled towards the mean
of the DV.
- Pre-test high scorers will appear to do poorer.
Pre-test low scorers will appear to do better.
- problem with unreliable measures
ie(7a)

16. Not a problem if the DV is very reliable.
ie(7a)

17. Confounds (in pre and post designs) History Maturation Instrumentation
Internal Validity?
Confounds (in pre and post designs)
History
Maturation
Instrumentation
Testing
Attrition (Mortality)
Statistical Regression Artifact*
ie(7a)

18. Controlling for these confounds. Use a pre-post control group.
Treated the same as treatment Group except
IV is not manipulated between tests.
Control group affected by same, history,
Maturation and Regression effects. Any difference between the treatment and control groups are not due to confounds.
ie(7a)

19. Pre-test Treatment Post-test plus confounds Control Group
Experimental Group
Pre-test Treatment Post-test
plus confounds
Control Group
Pre-test confounds Post-test
ie(7a)

20. Compare Pre-test scores. Are they the same to begin with?
Selection – confound due to assignment of subjects to the Control and Treatment Groups.
Compare Pre-test scores. Are they the same to begin with?
But could be a difference that interacts with the treatment.
- use random assignment!!!!
ie(7a)

21. subjects assigned to treatment and control group
Selection Confound
subjects assigned to treatment and control group
biased on a criteria (bias).
Selection X (interactions)
Any of the five confounds effect the control group
differently than the treatment group.
i.e., Alcohol treatment study
- compare volunteers to non-volunteers
e.g., Differential History
ie(7a)

22. Differential Attrition
Selection X (interactions)
Any of the five confounds effect the control group
differently than the treatment group.
Differential History
Differential Attrition
i.e., Alcohol treatment study
- compare volunteers to non-volunteers
ie(7a)

23. Differential Attrition Weight loss Study (Diet and Exercise condition)
No-Treatment Control Group
Type of people that drop put of the study might depend on which study they are in.
ie(7a)

24. How can we ensure the subjects in each condition are comparable?
Random Assignment
Extraneous variables still effect DV, but it
should not be a confound.
ie(7a)

25. Treatment group = size of treatment effect plus confounds
Pre-test
Post test
Treatment
Control
Treatment group = size of treatment effect plus confounds
Control group = estimate of the size of pre-post confounds.
ie(7a)

26. Pre-test
Post test
Treatment
Control
Is the pre-post test change significantly greater in the Treatment Condition than in the control condition?
ie(7a)