OCT 18 Experimental Designs study

Confounding Variables

Variables that are intertwined with another variable making it impossible to determine which variable is responsible for the observed effect.

Internal Validity

The extent to which an experiment can establish cause-and-effect relationships by meeting the criteria of temporal precedence, covariation, and eliminating alternative explanations.

Independent Groups Design

Randomly assigned to only ONE level of the IV, also known as a between-subjects design.

Repeated Measures Design

Assigned to ALL levels of the independent variable, also known as a within-subjects design.

Matched Pairs Design

A design where participants are paired based on a certain characteristic, then randomly assign one of each pair to ONE level of the IV

Independent Variable

The variable that is manipulated or changed in an experiment to test its effects on the dependent variable.

Dependent Variable

The variable that is measured in an experiment to assess the effect of the independent variable.

Pretest-Posttest Design

Participants are randomlyassigned to independentvariable groups and aretested on the dependentvariable twice – oncebefore and once afterexposure to theindependent variable.

Solomon Four-Group Design

An experimental design that assesses the impact of a pretest by treating it as a second independent variable. Half of the participants receive the pre-test and the post-test◦ Half receive only the post-test.

Causal Statements

Conclusions drawn in an experiment that indicate one variable directly affects another, based on established evidence.

Posttest-Only Design

Participants are randomly assigned to independent variable groups and are tested on the dependent variable once

Pretest-Posttest Designs Advantages

1. Sample size is small; allows you to assess the equivalency of groups◦

2. When you need specific participants for the experiment◦

3. When the likelihood of dropout is high

Pretest-Posttest Designs Disadvantages

1. Can be time-consuming + awkward to administer◦

2. Can sensitize participants to what is being studied◦

3. Can reduce the extent to which results generalize to people who did not receive a pretest