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Introduction to Behavioral Research

Methods

Leary

Sixth Edition

Pearson Education Limited

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Harlow

Essex CM20 2JE

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British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library

Printed in the United States of America

ISBN 10: 1-292-02027-X

ISBN 13: 978-1-292-02027-3

ISBN 10: 1-292-02027-X

ISBN 13: 978-1-292-02027-3

Table of Contents

PEARSON C U S T OM LIBRAR Y

I

Glossary

1

1Mark R. Leary

1. Research in the Behavioral Sciences

15

15Mark R. Leary

2. Behavioral Variability and Research

45

45Mark R. Leary

3. The Measurement of Behavior

63

63Mark R. Leary

4. Approaches to Psychological Measurement

85

85Mark R. Leary

5. Selecting Research Participants

113

113Mark R. Leary

6. Descriptive Research

131

131Mark R. Leary

7. Correlational Research

155

155Mark R. Leary

8. Advanced Correlational Strategies

179

179Mark R. Leary

9. Basic Issues in Experimental Research

199

199Mark R. Leary

10. Experimental Design

231

231Mark R. Leary

11. Analyzing Experimental Data

253

253Mark R. Leary

12. Analyzing Complex Experimental Designs

273

273Mark R. Leary

II

13. Quasi-Experimental Designs

293

293Mark R. Leary

14. Single-Case Research

315

315Mark R. Leary

15. Ethical Issues in Behavioral Research

333

333Mark R. Leary

Appendix: Statistical Tables

357

357Mark R. Leary

Appendix: Computational Formulas for ANOVA

363

363Mark R. Leary

Appendix: Choosing the Proper Statistical Analysis

373

373Mark R. Leary

References

375

375Mark R. Leary

387

387Index

From Introduction to Behavioral Research Methods, Sixth Edition. Mark R. Leary. Copyright © 2012 by Pearson

Education, Inc. All rights reserved.

GLOSSARY

1

ABA design a single-case experimental design in which

baseline data are obtained (A), the independent variable is

introduced and behavior is measured again (B), then the

independent variable is withdrawn and behavior is

observed a third time (A)

ABACA design a multiple-I single-case experimental

design in which baseline data are obtained (A), one level

of the independent variable is introduced (B), this level of

the independent variable is withdrawn (A), a second level

of the independent variable is introduced (C), and this

level of the independent variable is withdrawn (A)

ABC design a multiple-I single-case experimental design

that contains a baseline period (A), followed by the intro-

duction of one level of the independent variable (B), fol-

lowed by the introduction of another level of the

independent variable (C)

abstract a summary of a journal article or research report

acquiescence the tendency for some people to agree with

statements regardless of their content

alpha level the maximum probability that a researcher is

willing to make a Type I error (rejecting the null hypothesis

when it is true); typically, the alpha level is set at .05

analysis of variance (ANOVA) an inferential statistical

procedure used to test differences between means

APA style guidelines set forth by the American Psycho-

logical Association (APA) for preparing research reports;

these guidelines may be found in the Publication Manual

of the American Psychological Association (6th ed.)

applied research research designed to investigate real-

world problems or improve the quality of life

a priori prediction a prediction made about the outcome

of a study before data are collected

archival research research in which data are analyzed

from existing records, such as census reports, court

records, or personal letters

attrition the loss of participants during a study

author–date system in APA style, the manner of citing

previous research by providing the author’s last name and

the date of publication

bar graph a graph of data on which the variable on the

x-axis is measured on a nominal or ordinal scale of

measurement; because the x-variable is not continuous, the

bars do not touch one another

basic research research designed to understand psycho-

logical processes without regard for whether that

understanding will be immediately applicable in solving

real-world problems

beta the probability of committing a Type II error (failing

to reject the null hypothesis when it is false)

between-groups variance the portion of the total variance

in a set of scores that reflects systematic differences between

the experimental groups

between-subjects or between-groups design an

experimental design in which each participant serves in

only one condition of the experiment

between-within design an experimental design that com-

bines one or more between-subjects factors with one or

more within-subjects factors; also called mixed factorial or

split-plot design

biased assignment a threat to internal validity that occurs

when participants are assigned to conditions in a nonrandom

manner, producing systematic differences among conditions

prior to introduction of the independent variable

Bonferroni adjustment a means of preventing inflation of

Type I error when more than one statistical test is

conducted; the desired alpha level (usually .05) is divided by

the number of tests to be performed

canonical variable in MANOVA, a composite variable

that is calculated by summing two or more dependent

variables that have been weighted according to their ability

to differentiate among groups of participants

carryover effects effects that may occur in a within-

subjects experiment when the effect of a particular level

of the independent variable persists even after the treat-

ment ends; carryover effects may lead researchers to

conclude that a particular level of the independent

variable had an effect on participants’ responses when

the effect was actually caused by a level that was admin-

istered earlier

case study an intensive descriptive study of a particular

individual, group, or event

checklist a measuring instrument on which a rater

indicates whether particular behaviors have been observed

class interval a subset of a range of scores; in a grouped

frequency distribution, the number of participants who fall

into each class interval is shown

GLOSSARY

2

cluster sampling a probability sampling procedure in

which the researcher first samples clusters or groups

of participants, and then obtains participants from the

selected clusters

coefficient of determination the square of the correlation

coefficient; indicates the proportion of variance in one

variable that can be accounted for by the other variable

coercion to participate the situation that arises when

people agree to participate in a research study because of

real or implied pressure from some individual who has

authority or influence over them

comparative time series design a quasi-experimental

design that examines two or more variables over time to

understand how changes in one variable are related

to changes in another variable; also called comparative

trend analysis

computerized experience sampling methods the use of

small, portable computers, personal digital assistants, or

smartphones to allow participants to record information

about experiences in their daily lives soon after they happen

conceptual definition an abstract, dictionary-type

definition (as contrasted with an operational definition)

concurrent validity a form of criterion-related validity

that reflects the extent to which a measure allows a

researcher to distinguish between respondents at the time

the measure is taken

condition one level of an independent variable

confederate an accomplice of an experimenter whom

participants assume to be another participant or an

uninvolved bystander

confidence interval (CI) the range of scores around

a sample mean in which the means of other samples

from the same population are likely to fall with a certain

probability (usually 95%)

confidentiality maintaining the privacy of participants’

responses in a study

confounding a condition that exists in experimental

research when something other than the independent

variable differs systematically among the experimental

conditions

confound variance the portion of the total variance in a

set of scores that is due to extraneous variables that differ

systematically between the experimental groups; also

called secondary variance

construct validity the degree to which a measure of a

particular construct correlates as expected with measures

of other constructs

contemporary history a threat to the internal validity of a

quasi-experiment that develops when another event occurs

at the same time as the quasi-independent variable

content analysis procedures used to convert written or

spoken information into data that can be analyzed and

interpreted

contrived observation the observation of behavior in set-

tings that have been arranged specifically for observing

and recording behavior

control group participants in an experiment who receive

a zero level of the independent variable

convenience sample a nonprobability sample that

includes whatever participants are readily available

convergent validity documenting the validity of a measure

by showing that it correlates appropriately with measures

of related constructs

converging operations using several measurement

approaches to measure a particular variable

correlational research research designed to examine the

nature of the relationship between two measured variables

correlation coefficient an index of the direction and

magnitude of the relationship between two variables; the

value of a correlation coefficient ranges from 21.00 to 11.00

cost–benefit analysis a method of making decisions in

which the potential costs and risks of a study are weighed

against its likely benefits

counterbalancing a procedure used in within-subjects

designs in which different participants receive the levels of

the independent variable in different orders; counter-

balancing is used to avoid systematic order effects

criterion-related validity the extent to which a measure

allows a researcher to distinguish among respondents on the

basis of some behavioral criterion

criterion variable the variable being predicted in a

regression analysis; the dependent or outcome variable

critical multiplism the philosophy that researchers should

use many ways of obtaining evidence regarding a particular

hypothesis rather than relying on a single approach

critical value the minimum value of a statistic (such as t

or F) at which the results would be considered statistically

significant

Glossary

3

Cronbach’s alpha coefficient an index of interitem relia-

bility

cross-lagged panel correlation design a research design in

which two variables are measured at two points in time and

correlations between the variables are examined across time

cross-sectional design a research design in which a group

of respondents is studied once

cross-sequential cohort design a quasi-experimental

design in which two or more age cohorts are measured at

two or more times; in essence, it is a longitudinal design

with multiple age groups that allows researchers to sepa-

rate the effects of age and cohort

debriefing the procedure through which research partici-

pants are told about the nature of a study after it is completed

deception misleading or lying to participants for research

purposes

deduction the process of reasoning from a general pro-

position to a specific implication of that proposition; for

example, hypotheses are often deduced from theories

demand characteristics aspects of a study that indicate to

participants how they are expected to respond

demographic research descriptive research that studies

basic life events in a population, such as patterns of births,

marriages, deaths, and migrations

deontology an ethical approach maintaining that right and

wrong should be judged according to a universal moral code

dependent variable the response measured in a study,

typically a measure of participants’ thoughts, feelings,

behavior, or physiological reactions

descriptive research research designed to describe in an

accurate and systematic fashion the behavior, thoughts, or

feelings of a group of participants

descriptive statistics numbers that summarize and

describe the behavior of participants in a study; the mean

and standard deviation are descriptive statistics, for example

diary methodology a method of data collection in which

participants keep a daily record of their behavior, thoughts,

or feelings

differential attrition the loss of participants during a

study in a manner such that the loss is not randomly

distributed across conditions

directional hypothesis a prediction that explicitly states

the direction of a hypothesized effect; for example, a pre-

diction of which two means will be larger

direct object identifier (doi) the unique number assigned

to a journal article that assists with its retrieval from

electronic databases and on-line sources

discriminant validity documenting the validity of a

measure by showing that it does not correlate with measures

of conceptually unrelated constructs

disguised observation observing participants’ behavior

without their knowledge

double-blind procedure the practice of concealing the

purpose and hypotheses of a study both from the partici-

pants and from the researchers who have direct contact

with the participants

duration a measure of the amount of time that a particular

reaction lasts from its onset to conclusion

economic sample a sample that provides a reasonable

degree of accuracy at a reasonable cost in terms of money,

time, and effort

effect size the strength of the relationship between two or

more variables, usually expressed as the proportion of

variance in one variable that can be accounted for by

another variable

empirical generalization a hypothesis that is based on

the results of previous studies

empiricism the practice of relying on observation to draw

conclusions about the world

environmental manipulation an independent variable

that involves the experimental modification of the partici-

pant’s physical or social environment

epidemiological research research that studies the

occurrence of disease in different groups of people

error bar a vertical line used in a bar graph or histogram

to indicate the confidence interval around a group mean

error of estimation the degree to which data obtained

from a sample are expected to deviate from the population

as a whole; also called margin of error

error variance that portion of the total variance in a set of

data that remains unaccounted for after systematic variance

is removed; variance that is unrelated to the variables under

investigation in a study

ESM see experience sampling method

ethical skepticism an ethical approach that denies the

existence of concrete and inviolate moral codes

evaluation research the use of behavioral research methods

to assess the effects of programs on behavior; also called

program evaluation

expericorr factorial design an experimental design that

includes one or more manipulated independent variables

and one or more preexisting participant variables that are

measured rather than manipulated; also called mixed facto-

rial design

experience sampling method (ESM) a method of col-

lecting data in which participants record information about

their thoughts, emotions, or behaviors as they occur in

everyday life

Glossary

4

experiment research in which the researcher assigns par-

ticipants to conditions and manipulates at least one

independent variable

experimental contamination a situation that occurs

when participants in one experimental condition are indi-

rectly affected by the independent variable in another

experimental condition because they interacted with

participants in the other condition

experimental control the practice of eliminating or

holding constant extraneous variables that might affect the

outcome of an experiment

experimental group participants in an experiment who

receive a nonzero level of the independent variable

experimental hypothesis the hypothesis that the

independent variable will have an effect on the dependent

variable; equivalently, the hypothesis that the means of

the various experimental conditions will differ from one

another

experimental research research designed to test whether

certain variables cause changes in behavior, thoughts, or

feelings; in an experiment, the researcher assigns partici-

pants to conditions and manipulates at least one independ-

ent variable

experimenter expectancy effect a situation in which a

researcher’s expectations about the outcome of a study

influence participants’ reactions; also called Rosenthal effect

experimenter’s dilemma the situation in which,

generally speaking, the greater the internal validity of an

experiment, the lower its external validity, and vice versa

external validity the degree to which the results obtained

in one study can be replicated or generalized to other

samples, research settings, and procedures

extreme groups procedure creating two groups of par-

ticipants that have unusually low or unusually high scores

on a particular variable

face validity the extent to which a measurement proce-

dure appears to measure what it is supposed to measure

factor (1) in experimental designs, an independent

variable; (2) in factor analysis, the underlying dimension

that is assumed to account for observed relationships

among variables

factor analysis a class of multivariate statistical techniques

that identifies the underlying dimensions (factors) that

account for the observed relationships among a set of

measured variables

factorial design an experimental design in which two or

more independent variables are manipulated

factor loading in factor analysis, the correlation between

a variable and a factor

factor matrix a table that shows the results of a factor

analysis; in this matrix the rows are variables and the

columns are factors

failing to reject the null hypothesis concluding on the

basis of statistical evidence that the null hypothesis is

true—that the independent variable does not have an effect

falsifiability the requirement that a hypothesis must be

capable of being falsified

fatigue effects effects that may occur in a within-subjects

experiment when participants’ performance declines

during the study because they become tired, bored, or

unmotivated as they serve in more than one experimental

condition; fatigue effects may lead researchers to conclude

that participants’ poor performance in a particular experi-

mental condition was due to the independent variable

when it was actually due to fatigue, disinterest, or lack of

motivation

field notes a researcher’s narrative record of a partici-

pant’s behavior

file drawer problem the possibility that studies that failed

to support a particular hypothesis have not been published,

leading researchers to overestimate the amount of support

for an effect based on only the published evidence

fit index in structural equations modeling, a statistic that

indicates how well a hypothesized model fits the data

fixed-alternative response format a response format in

which participants answer a questionnaire or interview

item by choosing one response from a set of possible alter-

natives; also called a multiple choice response format

fMRI see functional magnetic resonance imaging

follow-up tests inferential statistics that are used after a

significant F-test to determine which means differ from

which; also called post hoc tests or multiple comparisons

free-response format a response format in which the par-

ticipant provides an unstructured answer to a question;

also called an open-ended question

frequency the number of participants who obtained a

particular score

frequency distribution a table that shows the number

of participants who obtained each possible score on a

measure

frequency polygon a form of line graph

F-test an inferential statistical procedure used to test for

differences among condition means; the F-test is used in

ANOVA

Glossary

5

functional magnetic resonance imaging (fMRI) a

brain imaging technology that allows researchers to

view the structure and activity of the brain; used to study

the relationship between brain activity and psychologi-

cal phenomena, such as perception, thought, and

emotion

gender-neutral language language that treats men and

women equally and does not perpetuate stereotypes about

men and women

generational effects differences among people of

various ages that are due to the different conditions

under which each generation has grown up rather than

age differences

grand mean the mean of all of the condition means in an

experiment

graphical method presenting and summarizing data in

pictorial form (e.g., graphs and pictures)

graphic analysis in single-case experimental research,

the visual inspection of graphs of the data to determine

whether the independent variable affected the participant’s

behavior

group design an experimental design in which several

participants serve in each condition of the design, and the

data are analyzed by examining the average responses of

participants in these conditions

grouped frequency distribution a table that indicates the

number of participants who obtained each of a range of scores

hierarchical multiple regression a multiple regression

analysis in which the researcher specifies the order that

the predictor variables will be entered into the regression

equation

histogram a form of bar graph in which the variable on

the x-axis is on a continuous scale

history effects changes in participants’ responses between

pretest and posttest that are due to an outside, extraneous

influence rather than to the independent variable

hypothesis a proposition that follows logically from a

theory; also, a prediction regarding the outcome of a

study

hypothetical construct an entity that cannot be directly

observed but that is inferred on the basis of observable

evidence; intelligence, status, and anxiety are examples of

hypothetical constructs

idiographic approach research that describes, analyzes,

and attempts to understand the behavior of individual

participants; often contrasted with the nomothetic

approach

independent variable in an experiment, the variable that

is varied or manipulated by the researcher to assess its

effects on participants’ behavior

induction the process of reasoning from specific instances

to a general proposition about those instances; for example,

hypotheses are sometimes induced from observed facts

inferential statistics mathematical analyses that allow

researchers to draw conclusions regarding the reliability

and generalizability of their data; t-tests and F-tests are

inferential statistics, for example

informed consent the practice of informing participants

regarding the nature of their participation in a study and

obtaining their explicit consent to participate

informed consent form a document that describes the

nature of participants’ participation in a study (including

all possible risks) and provides an opportunity for

participants to indicate in writing their willingness to

participate

Institutional Review Board (IRB) a committee

mandated by federal regulations that must evaluate the

ethics of research conducted at institutions that receive

federal funding

instructional manipulation an independent variable that

is varied through verbal information that is provided to

participants

interaction the combined effect of two or more independ-

ent variables such that the effect of one independent

variable differs across the levels of the other independent

variable(s)

interbehavior latency the time that elapses between the

occurrence of two behaviors

interitem reliability the consistency of respondents’

responses on a set of conceptually related items; the degree

to which a set of items that ostensibly measure the same

construct are intercorrelated

internal validity the degree to which a researcher draws

accurate conclusions about the effects of an independent

variable

Internet survey a survey in which respondents

access and respond to research materials on the World

Wide Web

interparticipant replication in single-case experimental

research, documenting the generalizability of an experimental

effect by demonstrating the effect on other participants

interparticipant variance variability among the res-

ponses of the participants in a particular experimental

condition

Glossary

6

interrater reliability the degree to which the observa-

tions of two independent raters or observers agree; also

called interjudge or interobserver reliability

interrupted time series design with a reversal a study in

which (1) the dependent variable is measured several

times; (2) the independent variable is introduced; (3) the

dependent variable is measured several more times; (4) the

independent variable is then withdrawn; and (5) the dep-

endent variable is again measured several times

interrupted time series design with multiple replications

a study in which (1) the dependent variable is measured

several times; (2) the independent variable is introduced;

(3) the dependent variable is measured again; (4) the inde-

pendent variable is withdrawn; (5) the dependent variable is

measured; (6) the independent variable is introduced a second

time; (7) more measures of the dependent variable are taken;

(8) the independent variable is once again withdrawn; and

(9) the dependent variable is measured after the independent

variable has been withdrawn for the second time

interval scale a measure on which equal distances

between scores represent equal differences in the property

being measured

interview a method of data collection in which respon-

dents respond verbally to a researcher’s questions

interview schedule the series of questions and accom-

panying response formats that guides an interviewer’s line

of questioning during an interview

intraparticipant replication in single-case experimental

research, the attempt to repeatedly demonstrate an experi-

mental effect on a single participant by alternatively intro-

ducing and withdrawing the independent variable

intraparticipant variance variability among the responses

of a participant when tested more than once in a particular

experimental condition

invasion of privacy violation of a research participant’s right

to determine how, when, or where he or she will be studied

invasive manipulation an independent variable that

directly alters the participant’s body, such as surgical

procedures or the administration of chemical substances

item any prompt that leads a participant to provide an

answer, rating, or other verbal response on a questionnaire

or in an interview

item-total correlation the correlation between respondents’

scores on one item on a scale and the sum of their responses

on the remaining items; an index of interitem reliability

knowledgeable informant someone who knows a

participant well enough to report on his or her behavior

latency the amount of time that elapses between a particular

event and a behavior

Latin Square design an experimental design used to

control for order effects in a within-subjects design

level one value of an independent variable

local history effect a threat to internal validity in which

an extraneous event happens to one experimental group

that does not happen to the other groups

longitudinal design a study in which a single group of

participants is studied over time

main effect the effect of a particular independent vari-

able, ignoring the effects of other independent variables in

the experiment

manipulation check a measure designed to determine

whether participants in an experiment perceived different

levels of the independent variable differently

margin of error see error of estimation

matched random assignment a procedure for assigning

participants to experimental conditions in which par-

ticipants are first matched into homogeneous blocks and

then participants within each block are assigned randomly

to conditions

matched-subjects design an experimental design in

which participants are matched into homogeneous blocks,

and participants in each block are randomly assigned to

the experimental conditions

matched-subjects factorial design an experimental

design involving two or more independent variables in

which participants are first matched into homogeneous

blocks and then, within each block, are randomly assigned

to the experimental conditions

maturation changes in participants’ responses between

pretest and posttest that are due to the passage of time

rather than to the independent variable; aging, fatigue, and

hunger may produce maturation effects, for example

mean the mathematical average of a set of scores; the sum

of a set of scores divided by the number of scores

mean square between-groups an estimate of between-

groups variance calculated by dividing the sum of squares

between-groups by the between-groups degrees of free-

dom

mean square within-groups the average variance within

experimental conditions; the sum of squares within-groups

divided by the degrees of freedom within-groups

measurement error the deviation of a participant’s

observed score from his or her true score

Glossary

7

measures of central tendency descriptive statistics that

convey information about the average or typical score in a

distribution; the mean, median, and mode are measures of

central tendency

measures of variability descriptive statistics that convey

information about the spread or variability of a set of data;

the range, variance, and standard deviation are measures of

variability

median the score that falls at the 50th percentile; the

middle score in a rank-ordered distribution

median-split procedure assigning participants to two

groups depending on whether their scores on a particular

variable fall above or below the median of that variable

meta-analysis a statistical procedure used to analyze and

integrate the results of many individual studies on a single

topic

methodological pluralism the practice of using many dif-

ferent research approaches to address a particular question

minimal risk risk to research participants that is no

greater than they would be likely to encounter in daily life

or during routine physical or psychological examinations

misgeneralization generalizing results from a study to a

by choosing one response from a set of possible alternatives;

also called a fixed-alternative response format

multiple comparisons inferental statistics that are

used after a significant F-test to determine which means

differ from which; also called post hoc tests or follow-

up tests

multiple correlation coefficient the correlation between

one variable and a set of other variables; often used in

multiple regression to express the strength of the relation-

ship between the outcome variable and the set of predictor

variables

multiple-I design a single-case experimental design in

which levels of an independent variable are introduced one

at a time

multiple regression analysis a statistical procedure by

which an equation is derived that can predict one variable

(the criterion or outcome variable) from a set of other vari-

ables (the predictor variables)

multistage cluster sampling a variation of cluster sam-

pling in which large clusters of participants are sampled,

followed by smaller clusters from within the larger clus-

ters, followed by still smaller clusters, until participants

are sampled from the small clusters

Glossary

Index