Psychology Exam 3 Prep: Confounding variables and obscuring Variables ch.11

One-group/post test design:

• Pre-experimental research design in which a single group of participants is measured before and after an intervention or treatment.

Protest

Measure the outcome variable before the intervention

Treatment/ intervention

Apply the experimental manipulation

Post test

Measure the same outcome variable again after the intervention.

Six Potential Internal Validity threats in one group, Pretest/Posttest Designs

1) Maturation threats to internal validity

2) History threats to internal validity

3) Regression threats to internal validity

4) Attribution threats to internal validity

5)Testing threats to internal validity

6)Instrumentation threats to internal validity

Maturation threats:

A change in behavior that emerges more or less spontaneously OVERTIME (Maturation=Natural change overtime)

• Example: Children become better and faster at solving addition and subtraction problems as they get older.

History threat

External or historical events that affect most members of the treatment group at the same time as the treatment, making it unclear whether the change in the DV for the experimental group was the result of the treatment or the result of the historical factor.

Attribution threat

A reduction in participant numbers from pretest to posttest. Attribution is problematic when it is systematic.

Regression threat

A statistical concept in which extremely low or extremely high performance at Time 1 is likely to be less extreme at Time 2(I.e., closer to average).

Ex: If you’re in a really good mood or a really bad mood, due to regression you will probably be in a more moderate mood tomorrow.

Double Blind Study

A study in which neither the participants nor the researchers who evaluate them know who is in the treatment group and who is in the comparison group.

Instrumentation

refers to changes in the measurement tool or procedure.