9 Introduction to Simple Experiments

Question 1

Between-subjects design

Answer 1

Between-groups design.

Question 2

Carryover effects

Answer 2

Order effect.

Question 3

Congruent-measures design

Answer 3

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.

Question 4

Condition

Answer 4

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

Question 5

Confound

Answer 5

A potential alternative explanation for a research finding (a threat to internal validity).

Question 6

Control group

Answer 6

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

Question 7

Control variable

Answer 7

A potential variable that an experimenter holds constant on purpose.

Question 8

Counterbalancing

Answer 8

Presenting the levels of the independent variable to participants in different orders to control for order effects.

Question 9

Demand characteristics

Answer 9

Cues that lead participants to guess a study’s hypothesis or goals.

Question 10

Design confound

Answer 10

A second variable that happens to vary systematically along with the independent variable and therefore is an alternative explanation for the results.

Question 11

Independent-groups design

Answer 11

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.

Question 12

Latin square

Answer 12

A formal system of partial counterbalancing that ensures that each condition appears in each position at least once.

Question 13

Manipulation check

Answer 13

An extra dependent variable that researchers can include in an experiment to determine how well an experimental manipulation worked.

Question 14

Matched-groups design

Answer 14

An experimental design in which participants who are similar on some measured variable are grouped into sets and the members of each match that are then randomly assigned to different experimental conditions.

Question 15

Order effects

Answer 15

A threat to internal validity that occurs when people exposed to one condition changes how people react to a later condition.

Question 16

Partial counterbalancing

Answer 16

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

Question 17

Pilot study

Answer 17

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

Question 18

Placebo group

Answer 18

A control group that is exposed to an inert treatment (e.g., a sugar pill).

Question 19

Posttest-only design

Answer 19

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

Question 20

Power

Answer 20

The probability that the study will show a statistically significant results when some effect is truly present in the population.

Question 21

Practice effect

Answer 21

A type of order effect in which people’s performance improves over time because they become practiced at the depended measure (not because of the manipulation or treatment).

Question 22

Pretest/posttest design

Answer 22

An experiment with 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.

Question 23

Random assignment

Answer 23

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

Question 24

Repeated-measures design

Answer 24

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

Question 25

Selection effect

Answer 25

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

Question 26

Systematic variability

Answer 26

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

Question 27

Treatment group

Answer 27

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

Question 28

Unsystematic variability

Answer 28

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

Question 29

Within-groups design

Answer 29

Within-subjects design.

A study design in which each participant is presented with all levels of the independent variable.