Logic of Experiments and Types of Designs

These flashcards cover key concepts related to the logic of experiments, types of design, and validity issues in experimental research.

Independent Variable

Treatment in an experiment that is manipulated to observe its effect on the dependent variable.

Dependent Variable

The outcome being measured in an experiment, which may include behaviors, attitudes, or physical conditions.

Experimental Group

The group in an experiment that receives the treatment or manipulation.

Control Group

The group that does not receive the treatment in an experiment, used for comparison.

Pretest

Measurement of the dependent variable prior to the introduction of the treatment.

Posttest

Measurement of the dependent variable after the treatment has been introduced.

Random Assignment

Method for assigning subjects to groups to ensure that each subject has an equal chance of being assigned to any group.

Matching

Pairing subjects based on similarities in specific characteristics to ensure comparability between groups.

Double-Blind Experiment

An experiment in which neither the participants nor the experimenters know which group the subjects are assigned to.

Solomon Four-Group Design

A type of experimental design that includes pretests and posttests with two experimental groups and two control groups.

Internal Validity

The degree to which the treatment is the true causal factor producing change in the dependent variable.

Selection Bias

A threat to internal validity where subjects are not equivalent across groups.

Maturation

Biological, psychological, or emotional changes within the subjects that may affect the outcome during an experiment.

Testing

The effect of having been pretested on the subsequent posttest measurement.

Instrumentation

Changes in the measuring instrument or observers that can influence outcomes.

Contamination

When subjects in different groups communicate and learn about each other's treatments.

External Validity

The extent to which experimental findings can be generalized to settings outside the experiment.

Reactivity

Subjects' reactions to being studied, which may alter their behavior.

Placebo Effect

A phenomenon where subjects receiving a placebo respond as if they received the actual treatment.

Field Experiment

An experiment conducted in a natural setting, generally offering higher external validity but lower internal validity.