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Chapter 10 research methods

Terms in this set (35)

carryover effect
A type of order effect, in which some form of contamination carries over from one condition to the next.
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. Also called comparison condition.
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.
condition
One of the levels of the independent variable in an experiment.
confound
A general term for a potential alternative explanation for a research finding (a threat to internal validity).
control group
A level of an independent variable that is intended to represent "no treatment" or a neutral condition.
control variable
A potential variable that an experimenter holds constant on purpose.
counterbalancing
In an experiment, presenting the levels of the independent variable to participants in different sequences to control for order effects. See also full counterbalancing, partial counterbalancing.
demand characteristic
A threat to internal validity that occurs when some cue leads participants to guess a study's hypotheses or goals. Also called experimental demand.
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. Also called outcome variable. See also independent variable.
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.
experiment
A study in which one variable is manipulated and the other is measured.
full counterbalancing
A method of counterbalancing in which all possible condition orders are represented. See also counterbalancing, partial counterbalancing.
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. Also called between-subjects design or between-groups design.
independent variable
A variable that is manipulated in an experiment. In a multiple-regression analysis, a predictor variable used to explain variance in the criterion variable. See also dependent variable.
Latin square
A formal system of partial counterbalancing that ensures that each condition in a within-groups design appears in each position at least once
manipulated variable
A variable in an experiment that a researcher controls, such as by assigning participants to its different levels (values). See also measured variable.
manipulation check
In an experiment, an extra dependent variable researchers can include to determine how well an experimental manipulation worked.
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. Also called matching.
measured variable
A variable in an experiment whose levels (values) are observed and recorded. See also manipulated variable.
order effect
In a within-groups design, a threat to internal validity in which exposure to one condition changes participants' responses to a later condition. See also carryover effect, practice effect, fatigue effect, testing threat.
partial counterbalancing
A method of counterbalancing in which some, but not all, of the possible condition orders are represented. See also counterbalancing, full counterbalancing.
pilot study
A study completed before (or sometimes after) the study of primary interest, usually to test the effectiveness or characteristics of the manipulations.
placebo group
A control group that is exposed to an inert treatment (e.g., a sugar pill). Also called placebo control group.
posttest-only design
An experiment using an independent-groups design in which participants are tested on the dependent variable only once. Also called equivalent groups, posttest-only design.
power
The likelihood that a study will show a statistically significant result when some effect is truly present in the population; the probability of not making a Type II error when the null hypothesis is false.
practice effect
A type of order effect in which people's performance improves over time because they become practiced at the dependent measure (not because of the manipulation or treatment). See also fatigue effect, order effect, testing threat.
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.
random assignment
The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups.
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.
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.
systematic variability
In an experiment, the levels of a variable coinciding in some predictable way with experimental group membership, creating a potential confound. See also unsystematic variability.
treatment group
The participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention.
unsystematic variability
In an experiment, when levels of a variable fluctuate independently of experimental group membership, contributing to variability within groups. See also systematic variability.
within-groups design
An experimental design in which each participant is presented with all levels of the independent variable. Also called within-subjects design.
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