Chapter 10- research methods in psychology

Social norms

Widely held beliefs about what most people in a group believe or value.

experiment

A study in which at least one variable is manipulated and another is measured.

manipulated variable

A variable in an experiment that a researcher controls, such as by assigning participants to its different levels (values).

measured variable

A variable in a study whose levels (values) are observed and recorded.

independent variable

In an experiment, a variable that is manipulated; in a multiple-regression analysis, a predictor variable used to explain variance in the criterion variable.

condition

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

dependent variable

In an experiment, the variable that is measured. In a multiple-regression analysis, the single outcome, or criterion variable the researchers are most interested in understanding or predicting

control variable

In an experiment, a variable that a researcher holds constant on purpose.

comparison group

A group in an experiment whose levels on the independent variable differ from those of the treatment group in some intended and meaningful way.

control group

A level of an independent variable that is intended to represent “no treatment” or a neutral condition.

treatment group

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

placebo group

A control group in an experiment that is exposed to an inert treatment, such as a sugar pill.

confound

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

design confound

A threat to internal validity in an experiment in which a second variable happens to vary systematically along with the independent variable and therefore is an alternative explanation for the results.

systematic variability

In an experiment, a description of when the levels of a variable coincide in some predictable way with experimental group membership, creating a potential confound.

unsystematic variability

In an experiment, a description of when the levels of a variable fluctuate independently of experimental group membership, contributing to variability within groups.

selection effect

A threat to internal validity that occurs in an independent-groups design when the kinds of participants at one level of the independent variable are systematically different from those at the other level.

random assignment

The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups.

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.

independent-groups design

An experimental design in which different groups of participants are exposed to different levels of the independent variable, such that each participant experiences only one level of the independent variable.

within-groups design

An experimental design in which each participant is presented with all levels of the independent variable.

posttest-only design

An experiment using an independent-groups design in which participants are tested on the dependent variable only once.

pretest/posttest design

An experiment using an independent-groups design in which participants are tested on the key dependent variable twice: once before and once after exposure to the independent variable.

repeated-measures design

An experiment using a within-groups design in which participants respond to a dependent variable more than once, after exposure to each level of the independent variable.

concurrent-measures design

An experiment using a within-groups design in which participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable.

order effect

In a within-groups design, a threat to internal validity in which exposure to one condition changes participant responses to a later condition.

practice effect

A type of order effect in which participants' performance improves over time because they become practiced at the dependent measure (not because of the manipulation or treatment).

fatigue effect

A type of order effect in which participants' performance degrades over time because they become tired, not because of the manipulation or treatment.

carryover effect

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

counterbalancing

In a repeated-measures experiment, presenting the levels of the independent variable to participants in different sequences to control for order effects.

full counterbalancing

A method of counterbalancing in which all possible condition orders are represented.

partial counterbalancing

A method of counterbalancing in which some, but not all, of the possible condition orders are represented.

Latin square

A formal system of partial counterbalancing to ensure that every condition in a within-groups design appears in each position at least once.

demand characteristic

A cue that leads participants to guess a study's hypotheses or goals; a threat to internal validity.

manipulation check

In an experiment, an extra dependent variable researchers can include to determine how well a manipulation worked.

pilot study

A study completed before (or sometimes after) the study of primary interest, usually to test the effectiveness or characteristics of the manipulations.