PSYC 52A Exam 2 Study Guide: Chapters 10, 11, and 12

Comprehensive vocabulary flashcards covering experimental variables, criteria for causality, internal validity threats, independent-groups and within-groups designs, null effects, and factorial designs from PSYC 52A Exam 2.

Variable

Anything that can be manipulated (changed) or measured in an experiment.

Independent Variable (IV)

The variable the researcher manipulates to determine its effect on behavior; it represents the possible cause.

Dependent Variable (DV)

The variable the researcher measures to assess the effects of the independent variable; it represents the outcome.

Manipulated Variable

A variable controlled or changed by the researcher, serving as an independent variable.

Measured Variable

A variable observed and recorded rather than changed by the researcher, often acting as a dependent variable or as a non-manipulated participant variable.

Control Variables

Variables the researcher intentionally holds constant throughout the experiment to prevent alternative explanations and establish internal validity.

Levels of a Variable

The different conditions or values of a variable; for a manipulated IV, each level represents a different experimental condition.

Covariance

A criterion for causality requiring that the IV and DV vary together, demonstrated by a difference in the outcome between experimental conditions.

Temporal Precedence

A criterion for causality requiring the cause to occur before the effect; the researcher must manipulate the IV prior to measuring the DV.

Internal Validity

The confidence with which researchers can conclude that effects in the DV resulted from manipulation of the IV, ruling out alternative explanations.

Treatment Group (Experimental Group)

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

Control Group

A comparison group in an experiment that does not receive the experimental treatment.

Placebo Group

A group that receives an inactive treatment designed to look like the actual treatment, helping isolate the belief in receiving treatment from actual treatment effects.

Systematic Variability

Variability that occurs when a variable changes in a predictable way along with experimental group membership, which can create a design confound.

Unsystematic Variability

Random variability that fluctuates independently of experimental group membership and increases within-group variability without creating a confound.

Design Confound

An extra, uncontrolled variable that is tied to both the treatment/exposure and the outcome, providing an alternative explanation for the results.

Selection Effects

A threat to internal validity occurring when participants in different experimental groups are systematically different due to how they were selected, volunteered, or assigned.

Random Assignment

A method of assigning participants to experimental conditions by chance to create equivalent groups and reduce selection effects.

Matched Groups

A procedure where participants are paired or grouped based on a shared characteristic and then members of each pair are assigned to different conditions.

Order Effects

Threats in within-groups designs where participants' responses to one condition are systematically affected by earlier exposure to another condition.

Independent-Groups Design

An experimental design in which different groups of participants are placed into different levels of the IV, meaning each participant experiences only one level; also called between-groups or between-subjects.

Posttest-Only Design

An independent-groups design where participants are tested on the dependent variable only after receiving the treatment or experimental manipulation.

Pretest/Posttest Design

An experimental design in which participants are tested on the dependent variable both before and after the experimental manipulation to measure change over time.

Within-Groups Design

An experimental design in which each participant experiences all levels of the independent variable, allowing participants to serve as their own controls; also called within-subjects.

Repeated-Measures Design

A within-groups design where participants experience each level of the IV at different times, and the DV is measured more than once.

Concurrent-Measures Design

A within-groups design in which participants are exposed to different levels of the IV at the same time and their responses are measured simultaneously.

Practice Effects

A type of order effect occurring when a participant's performance improves or declines because they have already completed the task previously due to learning, practice, or fatigue.

Carryover Effects

A type of order effect occurring when something from an earlier condition carries over and influences performance in a subsequent condition.

Demand Characteristics

Cues that lead participants to infer the purpose or hypothesis of a study and alter their behavior in the direction they think the researcher expects.

Counterbalancing

Presenting the levels of the independent variable in different orders across participants to reduce order effects in a within-groups design.

Full Counterbalancing

A counterbalancing procedure in which every possible order of the experimental conditions is presented to participants.

Partial Counterbalancing

A counterbalancing method where only a subset of all possible condition orders is presented, typically used when there are many conditions.

Manipulation Check

An extra measure used in an experiment to determine whether the experimental manipulation worked as intended and to identify weak manipulations.

Pilot Study

A small preliminary study conducted before the actual experiment to identify problems with procedures, instructions, measures, or manipulations.

Maturation Threat

A threat to internal validity where participants naturally change over time (e.g., through development or aging), and those changes explain the difference in the DV.

History Threat

A threat to internal validity that occurs when an outside event affects participants during the study and accounts for changes in the DV.

Regression Threat (Regression to the Mean)

A threat to internal validity where extremely high or low performance at Time 1 is likely to be less extreme and move closer to the average at Time 2.

Attrition Threat

A threat to internal validity occurring when participants drop out of a study between pretest and posttest, especially when the dropout pattern is systematic.

Testing Threat

A threat to internal validity in which taking the pretest changes participants' performance on the posttest due to familiarity or recall.

Instrumentation Threat

A threat to internal validity occurring when the measuring instrument or measurement criteria change over time, such as observers becoming more lenient.

Observer Bias

A threat to internal validity occurring when researchers' expectations influence how they interpret, rate, or record participants' behavior.

Placebo Effect

An improvement that occurs because participants believe they are receiving an effective treatment rather than from the treatment's actual active components.

Selection-History Threat

A combined threat to internal validity where an outside event or factor systematically affects participants at only one level of the independent variable.

Selection-Attrition Threat

A combined threat to internal validity where participants in only one experimental group experience dropout, leaving groups that differ systematically.

Double-Blind Study

A study in which neither the participants nor the researchers who interact with them know which experimental condition participants are assigned to.

Double-Blind Placebo Control Study

A study incorporating a placebo group where neither the participants nor the researchers interacting with them know who receives the real treatment and who receives the placebo.

Null Effect

An outcome occurring when a researcher does not find evidence of a statistically significant difference between experimental conditions.

Ceiling Effect

A measurement problem where scores cluster at the high end of the scale, leaving little room for scores to increase.

Floor Effect

A measurement problem where scores cluster at the low end of the scale, leaving little room for scores to decrease.

Measurement Error

Factors that inflate or deflate a person's true score on the dependent variable, contributing to excessive within-groups variability.

Situation Noise

External distractions or environmental variability that cause noise within groups and obscure differences between experimental conditions.

Factorial Design

An experiment that includes two or more independent variables (factors) to examine their individual effects and whether the effect of one IV depends on another.

Cell

One experimental condition in a factorial design representing a unique combination of the independent variables.

Factorial Notation

A numbering system (e.g., $2 \times 3$) where the number of digits reflects the number of IVs, each digit represents the levels of that IV, and their product equals total conditions.

Main Effect

The overall effect of one independent variable on the dependent variable, averaging across the levels of the other independent variable(s).

Marginal Means

The arithmetic averages for each level of an independent variable calculated by averaging over the levels of the other independent variable(s).

Interaction Effect

An effect occurring when the effect of one independent variable on the dependent variable depends on the level of another independent variable; described as a difference in differences.

Moderator

An independent variable that changes the relationship between another independent variable and the dependent variable, resulting in an interaction.