Chapter 8

experimental group

The group in an experiment that receives the treatment of interest.

control group

The comparison group used to evaluate causal claims in an experimental design.

covariation

The extent to which changes in one variable are associated with changes in another variable.

effect size

A standardized measure to represent the magnitude of the differences between groups on the dependent variable.

experimental control

Involves holding constant or accounting for factors other than the variable under investigation.

experimental hypothesis

The research hypothesis or prediction being tested in a study.

experimental realism

How engaged participants are in the study, making their reactions natural.

extraneous variable

Any factor other than the independent variable that may influence participants' responses.

independence

The responses of each participant are not influenced by nor influence other participants' responses.

internal validity

The degree to which one can rule out plausible rival hypotheses that could account for observed results.

manipulation check

A strategy for evaluating how effectively the manipulation creates differences between the levels of the independent variable.

matched-pair design

Groups participants based on a characteristic related to the outcome variable before random assignment.

mundane realism

The extent to which the study reflects everyday situations occurring in the real world.

null hypothesis

The hypothesis of no difference, usually the focus of a statistical test.

random assignment

A method assigning participants to experimental conditions in a nonsystematic and nonbiased manner.

t-test for independent means

A statistical test that compares the means of two different groups.

temporal precedence

Evidence that changes in the proposed causal variable occur before changes in the outcome variable.

two-group design

The most basic type of experimental design involving only two groups: a treatment and a comparison group.

researcher notes

written record of any unusual or unexpected occurrences that happened while running research

t-test for independent samples

statistical test compares the means of two different groups to determine if there is a significant difference between them.