Chapter 10 - Introduction to Simple Experiments

Question 1

Experiment

Answer 1

A study in which one variable is manipulated and the other is measured. (page 276)

Question 2

Manipulated Variable

Answer 2

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)

Question 3

Measured Variable

Answer 3

A variable in a study whose levels (values) are observed and recorded. See also manipulated variable. (page 277)

Question 4

Independent Variable

Answer 4

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)

Question 5

Condition

Answer 5

One of the levels of the independent variable in an experiment. (page 277)

Question 6

Dependent Variable

Answer 6

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)

Question 7

Control Variable

Answer 7

In an experiment, a variable that a researcher holds constant on purpose. (page 278)

Question 8

Comparison Group

Answer 8

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)

Question 9

Control Group

Answer 9

A level of an independent variable that is intended to represent “no treatment” or a neutral condition. Also called control condition. (page 280)

Question 10

Treatment Group

Answer 10

The participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention. (page 280)

Question 11

Placebo Group

Answer 11

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)

Question 12

Confound

Answer 12

A general term for a potential alternative explanation for a research finding; a threat to internal validity. (page 281)

Question 13

Design Confound

Answer 13

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)

Question 14

Systematic Variability

Answer 14

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)

Question 15

Unsystematic Variability

Answer 15

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)

Question 16

Selection Effect

Answer 16

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)

Question 17

Random Assignment

Answer 17

The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups. (page 284)

Question 18

Matched Groups

Answer 18

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)

Question 19

Independent-groups Design

Answer 19

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)

Question 20

Within-groups Design

Answer 20

An experimental design in which each participant is presented with all levels of the independent variable. Also called within-subjects design. (page 287)

Question 21

Posttest-only Design

Answer 21

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)

Question 22

Pretest/Posttest Design

Answer 22

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)

Question 23

Repeated-measures Design

Answer 23

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)

Question 24

Concurrent-measures Design

Answer 24

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)

Question 25

Power

Answer 25

The likelihood that a study will show a statistically significant result when an independent variable truly has an effect in the population; the probability of not making a Type II error. (page 293)

Question 26

Order Effect

Answer 26

In a within-groups design, a threat to internal validity in which exposure to one condition changes participant responses to a later condition. See also carryover effect, practice effect, testing threat. (page 294)

Question 27

Practice Effect

Answer 27

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). Also called fatigue effect. See also order effect, testing threat. (page 294)

Question 28

Carryover Effect

Answer 28

A type of order effect, in which some form of contamination carries over from one condition to the next. (page 294)

Question 29

Counterbalancing

Answer 29

In a repeated-measures experiment, presenting the levels of the independent variable to participants in different sequences to control for order effects. See also full counterbalancing, partial counterbalancing. (page 295)

Question 30

Full Counterbalancing

Answer 30

A method of counterbalancing in which all possible condition orders are represented. See also counterbalancing, partial counterbalancing. (page 295)

Question 31

Partial Counterbalancing

Answer 31

A method of counterbalancing in which some, but not all, of the possible condition orders are represented. See also counterbalancing, full counterbalancing. (page 296)

Question 32

Latin Square

Answer 32

A formal system of partial counterbalancing to ensure that every condition in a within-groups design appears in each position at least once. (page 296)

Question 33

Demand Characteristic

Answer 33

A cue that leads participants to guess a study’s hypotheses or goals; a threat to internal validity. Also called experimental demand. (page 297)

Question 34

Manipulation Check

Answer 34

In an experiment, an extra dependent variable researchers can include to determine how well a manipulation worked. (page 299)

Question 35

Pilot Study

Answer 35

A study completed before (or sometimes after) the study of primary interest, usually to test the effectiveness or characteristics of the manipulations. (page 300)