Experimental Psychology Exam 3

Attrition

The loss of participants over time in a study.

Baseline

The initial set of measurements taken at the beginning of a study before any experimental manipulation has been applied.

Carryover Effects

An order effect in which some form of contamination carries over from one condition to the next.

Comparison Group

A group in an experiment whose level of the independent variable differs from that of the treatment group in some intended and meaningful way.

Control Group

The group in an experiment that does not receive the treatment and serves as a comparison for evaluating the effect of the treatment.

Counterbalancing

A method in experimental design to control for order effects by ensuring that each condition appears in each position equally often.

Demand Characteristics

Cues in an experiment that tell the participant what behavior is expected.

Dependent Variable

The outcome factor; the variable that may change in response to manipulations of the independent variable.

Double-Blind Study

An experimental procedure in which both the participants and the research staff are ignorant about whether the participants have received the treatment or a placebo.

Experimental Group

The group in an experiment that receives the variable being tested.

Independent Variable

The experimental factor that is manipulated; the variable whose effect is being studied.

Internal Validity

The degree to which an experiment supports clear causal conclusions by controlling for confounding variables.

Matched Groups

An experimental design technique in which participants who are similar on some measured variable are grouped into sets; the members of each matched set are then randomly assigned to different experimental conditions.

Order Effects

Changes in participants' responses that result from the order in which the experimental materials are presented to them.

Placebo Effect

The phenomenon in which the expectations of the participants in a study can influence their behavior.

Random Assignment

Assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between those assigned to the different groups.

Regression to the Mean

The tendency for extreme or unusual scores to fall back (regress) toward their average.

Single-Blind Study

A study in which the participants are unaware whether they are in the control or experimental group, but the researchers know.

Statistical Significance

A statistical statement of the likelihood that an obtained result occurred by chance.

Treatment Group

The participants in an experiment who are exposed to the independent variable level that involves a medication, therapy, or intervention.

Within-Subjects Design

An experimental design in which the same subjects are tested under each condition.

Between-Subjects Design

An experimental design in which different groups of participants are exposed to different independent variable levels.

Cell

A specific condition or group in a factorial design experiment.

Condition

One of the different levels of the independent variable in an experiment.

Confederate

An actor who is directed by the researcher to play a specific role in a research study.

Confound

A general term for a potential alternative explanation for a research finding; a threat to internal validity.

Experimenter Bias

A bias that occurs when a researcher's expectations about the outcome of a study influence the results obtained.

Factorial Design

An experimental design involving two or more independent variables.

Interaction Effect

When the effect of one independent variable depends on the level of another independent variable.

Posttest-Only Design

An experimental design in which the dependent variable is measured only once after manipulating the independent variable.

Pretest-Posttest Design

An experimental design in which the dependent variable is measured before and after manipulating the independent variable.

Condition

One of the different levels of the independent variable in an experiment.

Within-Groups Design

An experimental design in which each participant is presented with all independent variable levels. Also called within-subjects design.