Chapter 10 - Introduction to Simple Experiments Flashcards
Experiment
A study in which one variable is manipulated and the other is measured. (page 276)
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. (page 276)
Measured Variable
A variable in a study whose levels (values) are observed and recorded. See also manipulated variable. (page 277)
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. See also dependent variable. (page 277)
Condition
One of the levels of the independent variable in an experiment. (page 277)
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. (page 277)
Control Variable
In an experiment, a variable that a researcher holds constant on purpose. (page 278)
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. (page 279)
Control Group
A level of an independent variable that is intended to represent “no treatment” or a neutral condition. Also called control condition. (page 280)
Treatment Group
The participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention. (page 280)
Placebo Group
A control group in an experiment that is exposed to an inert treatment, such as a sugar pill. Also called placebo control group. (page 280)
Confound
A general term for a potential alternative explanation for a research finding; a threat to internal validity. (page 281)
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. (page 282)
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. See also unsystematic variability. (page 282)
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. See also systematic variability. (page 282)
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. (page 284)
Random Assignment
The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups. (page 284)
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. (page 286)
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. (page 287)
Within-groups Design
An experimental design in which each participant is presented with all levels of the independent variable. Also called within-subjects design. (page 287)
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. (page 287)
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. (page 288)
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. (page 290)
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. (page 291)
