Confounds
A reduction in participant numbers from pretest to posttest.
Attrition threat
one group of participants is measured on a pretest, exposed to a treatment, intervention, or change, and then measured on a posttest.
One-group pretest/posttest design
How are maturation threats prevented?
Add a control group
An experiment in which there are two or more IVs
Factorial design
The independent variable did not affect the dependent variable, so there is no significant covariance between the IV and the DV.
Null effect
When an extreme finding is caused by a combination of random factors that are unlikely to happen in the same combination again, so the extreme finding becomes less extreme over time
Regression threat
Researchers stagger their interventions across situations, times, or contexts.
Multiple-baseline designs
Daily Double!
How are history threats avoided?
An _______ effect occurs when the effect of one IV depends on the level of another IV.
interaction
(Error Variance) too much unsystematic variability within groups.
Noise
Bias caused by researchers’ expectations influencing how they interpret the results.
Observer bias
One IV is manipulated as independent-groups and the other is manipulated within-groups.
Mixed Factorial Design
How can attrition threats be prevented?
When participants drop out of a study, remove their scores from the pretest average.
The IVs in a factorial design are also called
factors
The participants’ scores on the DV are clustered at the high end
Ceiling effect
A change in behavior that emerges spontaneously over time.
Maturation threats
Participants are not randomly assigned to groups and are tested only once, after exposure to either one level of the independent variable or the other.
nonequivalent control group posttest-only design
How can instrumentation threats be prevented?
–Use a posttest-only design
–counterbalance the order of the pretest and posttest forms
This is the overall effect of one IV on the DV, averaging over levels of the other IV, and it identifies a simple difference.
Main effect
The participants’ scores on the DV are clustered at the low end.
Floor effect
What is the key difference between Instrumentation threats versus Testing threats
Instrumentation threats are when the instruments change over time. Testing threats are when participants change over time.
a special comparison group is used that is receiving the placebo therapy or placebo medication, but neither the people working with the participants nor the participants know who is in which group
Double-blind placebo control study
How can testing threats be prevented?
Use a Posttest design (no pretest)
Use alternative forms of the test at pretest and posttest
Are the differences in differences different?
Three-way interactions
Any factor that can inflate or deflate a person’s true score on the DV.
Measurement error