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272 Cards in this Set

  • Front
  • Back

abstract

A brief description of a completed or proposed study, usually located at the beginning of a
report or proposal.


accessible population

The population of people available for a particular study; often a nonrandom
subset of the target population.


accidental sampling

Selection of the most readily available people as study participants; also called
convenience sampling.

acquiescence response set

A bias in self-report instruments, especially in psychosocial scales,
created when participants characteristically agree with statements (“yea-say”) independent of content.

after-only design

An experimental design in which data are collected from subjects only after an
intervention has been introduced.


allocation concealment

The process used to ensure that those enrolling subjects into a clinical trial
are unaware of upcoming assignments, that is, the treatment group to which new enrollees will be assigned.


alpha

(1) In tests of statistical significance, the level indicating the probability of a Type I error;
(2) in assessments of internal consistency reliability, a reliability coefficient, Cronbach’s alpha.


alternative hypothesis

In hypothesis testing, a hypothesis different from the one being tested—usually, different from the null hypothesis.

analysis of covariance (ANCOVA)

A statistical procedure used to test mean differences among
groups on a dependent variable, while controlling for one or more covariates.


analysis of variance (ANOVA)

A statistical procedure for testing mean differences among three or
more groups by comparing variability between groups to variability within groups.

anonymity

Protection of participants’ confidentiality such that even the researcher cannot link
individuals with information provided.

arm

A group of participants allocated a particular treatment (e.g., the control arm or treatment
arm).


associative relationship

An association between two variables that cannot be described as causal
(i.e., one variable causing the other).

asymmetric distribution

A distribution of data values that is skewed, with two halves that are not
mirror images of each other.

attention control group

A control group that gets a similar amount of attention to those in the
intervention group, without the “active ingredients” of the treatment.


attribute variables

Preexisting characteristics of study participants, which the researcher simply
observes or measures.

attrition

The loss of participants over the course of a study, which can create bias by changing the
composition of the sample initially drawn.


baseline data

Data collected prior to an intervention, including pretreatment data measuring the
dependent variables.


before–after design

An experimental design in which data are collected from subjects both before
and after the introduction of an intervention.

beta
(1) In multiple regression, the standardized coefficients indicating the relative weights of the predictor variables in the equation; (2) in statistical testing, the probability of a Type II error.

between-subjects design

A research design in which there are separate groups of people being
compared (e.g., smokers and nonsmokers).


bias

Any influence that distorts the results of a study and undermines validity.

blind review

The review of a manuscript or proposal such that neither the author nor the reviewer
is identified to the other party.

blinding

The process of preventing those involved in a study (subjects, intervention agents, or data
collectors) from having information that could lead to a bias, for example, knowledge of which
treatment group a subject is in; also called masking.


Bonferroni correction

An adjustment made to establish a more conservative alpha level when
multiple statistical tests are being run from the same data set; the correction is computed by dividing
the desired α by the number of tests—e.g., .05/3 = .017.

carry-over effect

The influence that one treatment can have on subsequent treatments.

case-control design

A nonexperimental research design involving the comparison of a “case” (i.e., a
person with the condition under scrutiny, such as lung cancer) and a matched control (a similar
person without the condition).


categorical variable

A variable with discrete values (e.g., gender) rather than values along a
continuum (e.g., weight).

causal (cause-and-effect) relationship

A relationship between two variables such that the
presence or absence of one variable (the “cause”) determines the presence or absence (or value) of
the other (the “effect”).


central tendency

A statistical index of the “typicalness” of a set of scores, derived from the center of
the score distribution; indices of central tendency include the mode, median, and mean.


chi-square test

A statistical test used to assess differences in proportions; symbolized as 2.

clinical relevance

The degree to which a study addresses a problem of significance to the practice of
nursing.

clinical trial

A study designed to assess the safety, efficacy, and effectiveness of a new clinical
intervention, sometimes involving several phases (e.g., Phase III is a randomized clinical trial using an
experimental design).


closed-ended question

A question that offers respondents a set of mutually exclusive response
options.

cluster randomization

The random assignment of intact groups of subjects—rather than individual
subjects—to treatment conditions.


cluster sampling

A form of sampling in which large groupings (“clusters”) are selected first (e.g.,
nursing schools), with successive subsampling of smaller units (e.g., nursing students).

coefficient alpha (Cronbach’s alpha)

A reliability index that estimates the internal consistency or
homogeneity of a measure composed of several items or subparts.

cohort design

A nonexperimental design in which a defined group of people (a cohort) is followed
over time to study outcomes for subsets of the cohorts; also called a prospective design.


cohort study

A kind of trend study that focuses on a specific subpopulation (which is often an agerelated subgroup) from which different samples are selected at different points in time (e.g., the cohort of nursing students who graduated between 1970 and 1974).

comparison group

A group of subjects whose scores on a dependent variable are used to evaluate
the outcomes of the group of primary interest (e.g., nonsmokers as a comparison group for smokers);
term used in lieu of control group when the study design is not a true experiment.


concurrent validity

The degree to which scores on an instrument are correlated with an external
criterion, measured at the same time.


confidence interval (CI)

The range of values within which a population parameter is estimated to
lie, at a specified probability (e.g., 95% CI).


confidentiality

Protection of study participants so that data provided are never publicly divulged.

confirmatory factor analysis (CFA)

A factor analysis designed to confirm a hypothesized
measurement model, using maximum likelihood estimation.

confounding variable

A variable extraneous to the research question that confounds or potentially
obscures the relationship between the independent and dependent variable and that should be
controlled.


construct validity

The validity of inferences from observed persons, settings, and interventions in a
study to the constructs that these instances might represent; with an instrument, the degree to which
it measures the construct under investigation.


contamination

The inadvertent, undesirable influence of one treatment condition on another
treatment condition.

content validity

The degree to which the items in an instrument adequately represent the universe
of content for the concept being measured.

continuous variable

A variable that can take on an infinite range of values along a specified
continuum (e.g., height)

control group

Subjects in an experiment who do not receive the experimental treatment and whose
performance provides a baseline against which the effects of the treatment can be measured (see also
comparison group).


controlled trial

A trial that has a control group, with or without randomization.

convenience sampling

Selection of the most readily available persons as participants in a study;
also called accidental sampling.


convergent validity

An approach to construct validation that involves assessing the degree to which
two methods of measuring a construct are similar (i.e., converge).


correlation

An association or bond between variables, with variation in one variable systematically
related to variation in another.

correlation coefficient

An index summarizing the degree of relationship between variables,
typically ranging from +1.00 (for a perfect positive relationship) through 0.0 (for no relationship) to –
1.00 (for a perfect negative relationship).


correlational research

Research that explores the interrelationships among variables of interest
without researcher intervention.

counterfactual

The condition or group used as a basis of comparison in a study, embodying what
would have happened to the same people exposed to a causal factor if they simultaneously were not
exposed to the causal factor

covariate

A variable that is statistically controlled (held constant) in ANCOVA, typically an
extraneous influence on, or a preintervention measure of, the dependent variable.


criterion-related validity

The degree to which scores on an instrument are correlated with some
external criterion.

Cronbach’s alpha

A widely used reliability index that estimates the internal consistency of a
measure composed of several subparts; also called coefficient alpha.

crossover design

An experimental design in which one group of subjects is exposed to more than
one condition or treatment in random order

cross-sectional design

A study design in which data are collected at one point in time; sometimes
used to infer change over time when data are collected from different age or developmental groups.

data triangulation

The use of multiple data sources for the purpose of validating conclusions.

Delphi survey

A technique for obtaining judgments from an expert panel about an issue of concern;
experts are questioned individually in several rounds, with a summary of the panel’s views circulated
between rounds, to achieve some consensus.


dependent variable

The variable hypothesized to depend on or be caused by another variable (the
independent variable); the outcome variable of interest.


descriptive research

Research that has as its main objective the accurate portrayal of the
characteristics of persons, situations, or groups, and/or the frequency with which certain phenomena
occur.


dichotomous variable

A variable having only two values or categories (e.g., gender).

discriminant validity

An approach to construct validation that involves assessing the degree to
which a single method of measuring two constructs yields different results (i.e., discriminates the
two).


double-blind experiment

An experiment in which neither the subjects nor those who administer
the treatment know who is in the experimental or control group.


effectiveness study

A clinical trial designed to shed light on effectiveness of an intervention under
ordinary conditions, with an intervention already found to be efficacious in an efficacy study

efficacy study

A tightly controlled clinical trial designed to establish the efficacy of an intervention
under ideal conditions, using a design that stresses internal validity.


eligibility criteria

The criteria designating the specific attributes of the target population, by which
people are selected for inclusion in a study.


exclusion criteria

The criteria that specify characteristics that a population does not have.

experiment

A study in which the researcher controls (manipulates) the independent variable and
randomly assigns subjects to different conditions.

experimental group

The subjects who receive the experimental treatment or intervention.

external validity

The degree to which study results can be generalized to settings or samples other
than the one studied.


F-ratio

The statistic obtained in several statistical tests (e.g., ANOVA) in which variation attributable
to different sources (e.g., between groups and within groups) is compared.

face validity

The extent to which a measuring instrument looks as though it is measuring what it
purports to measure.


factor analysis

A statistical procedure for reducing a large set of variables into a smaller set of
variables with common underlying dimensions.


factor loading

In factor analysis, the weight associated with a variable on a given factor.


factorial design

An experimental design in which two or more independent variables are
simultaneously manipulated, permitting a separate analysis of the main effects of the independent
variables and their interaction.

findings

The results of the analysis of research data.

Fisher’s exact test

A statistical procedure used to test the significance of the difference in
proportions, used when the sample size is small or cells in the contingency table have no
observations.


follow-up study

A study undertaken to determine the outcomes of individuals with a specified
condition or who have received a specified treatment.

frequency distribution

A systematic array of numeric values from the lowest to the highest,
together with a count of the number of times each value was obtained.


generalizability

The degree to which the research methods justify the inference that the findings
are true for a broader group than study participants; in particular, the inference that the findings can
be generalized from the sample to the population

Hawthorne effect

The effect on the dependent variable resulting from subjects’ awareness that they
are participants under study.


heterogeneity

The degree to which objects are dissimilar (i.e., characterized by variability) on some
attribute.

histogram

A graphic presentation of frequency distribution data.

homogeneity

(1) In terms of the reliability of an instrument, the degree to which its subparts are
internally consistent (i.e., are measuring the same critical attribute). (2) More generally, the degree to
which objects are similar (i.e., characterized by low variability).


hypothesis

A statement of predicted relationships between variables.


impact factor

An annual measure of citation frequency for an average article in a given journal, that
is, the ratio between citations and recent citable items published in the journal.


IMRAD format

The organization of a research report into four sections: the Introduction, Method,
Research, and Discussion sections.

incidence rate
The rate of new cases with a specified condition, determined by dividing the number of new cases over a given period of time by the number at risk of becoming a new case (i.e. free of the condition at the outset of the time period).

independent variable

The variable that is believed to cause or influence the dependent variable; in
experimental research, the manipulated (treatment) variable.


informed consent

An ethical principle that requires researchers to obtain the voluntary
participation of subjects, after informing them of possible risks and benefits.

instrument

The device used to collect data (e.g., a questionnaire, test, observation schedule, etc.).


instrumentation threat

The threat to the internal validity of the study that can arise if the
researcher changes the measuring instrument between two points of data collection.


intention to treat

A strategy for analyzing data in an intervention study that includes participants
with the group to which they were assigned, whether or not they received or completed the
treatment associated with the group.


interaction effect

The effect of two or more independent variables acting in combination
(interactively) on a dependent variable.


internal consistency

The degree to which the subparts of an instrument are all measuring the same
attribute or dimension, as a measure of the instrument’s reliability.

internal validity
The degree to which it can be inferred that the experimental treatment (independent variable), rather than uncontrolled, extraneous factors, is responsible for observed
effects.

interrater (interobserver) reliability

The degree to which two raters or observers, operating
independently, assign the same ratings or values for an attribute being measured or observed.

interrupted time series design

See time series design

intervention

In experimental research, the experimental treatment or manipulation.

judgmental sampling

A type of nonprobability sampling method in which the researcher selects
study participants based on personal judgment about who will be most representative or
informative; also called purposive sampling.


kappa

An index used to measure interrater agreement, which summarizes the extent of agreement
beyond the level expected to occur by chance.


keyword

An important term used to search for references on a topic in a bibliographic database.


known-groups technique

A technique for estimating the construct validity of an instrument
through an analysis of the degree to which the instrument separates groups predicted to differ based
on known characteristics or theory.


Kruskal-Wallis test

A nonparametric test used to test the difference between three or more
independent groups, based on ranked scores.


level of measurement

A system of classifying measurements according to the nature of the
measurement and the type of permissible mathematical operations; the levels are nominal, ordinal,
interval, and ratio.

level of significance

The risk of making a Type I error in a statistical analysis, established by the
researcher beforehand (e.g., the .05 level).


Likert scale

A composite measure of attitudes involving the summation of scores on a set of items
that respondents rate for their degree of agreement or disagreement.


linear regression

An analysis for predicting the value of a dependent variable from one or more
predictors by determining a straight-line fit to the data that minimizes deviations from the line.


logistic regression

A multivariate regression procedure that analyzes relationships between one or
more independent variables and categorical dependent variables; also called logit analysis

longitudinal study

A study designed to collect data at more than one point in time, in contrast to a
cross-sectional study.


main effects

In a study with multiple independent variables, the effects of a single independent
variable on the dependent variable.


manipulation

An intervention or treatment introduced by the researcher in an experimental or
quasi-experimental study to assess its impact on the dependent variable.


Mann-Whitney U test

A nonparametric statistic used to test the difference between two
independent groups, based on ranked scores.


masking

See Blinding

matching

The pairing of subjects in one group with those in another group based on their similarity
on one or more dimension, to enhance the overall comparability of groups.

maturation threat

A threat to the internal validity of a study that results when changes to the
outcome measure (dependent variable) result from the passage of time.


McNemar test

A statistical test for comparing differences in proportions when values are derived
from paired (nonindependent) groups.

mean

A measure of central tendency, computed by summing all scores and dividing by the number
of subjects.

measurement

The assignment of numbers to objects according to specified rules to characterize
quantities of some attribute.


median

A descriptive statistic that is a measure of central tendency, representing the exact middle
value in a score distribution; the value above and below which 50 percent of the scores lie.


missing values

Values missing from a data set for some study participants, due, for example, to
refusals, errors, or skip patterns.


mixed method research

Research in which both qualitative and quantitative data are collected and
analyzed.


mortality threat

A threat to the internal validity of a study, referring to the differential loss of
participants (attrition) from different groups.

multistage sampling

A sampling strategy that proceeds through a set of stages from larger to
smaller sampling units (e.g., from states, to census tracts, to households).


multivariate analysis of variance (MANOVA)

A statistical procedure used to test the significance of
differences between the means of two or more groups on two or more dependent variables,
considered simultaneously.


negative relationship

A relationship between two variables in which there is a tendency for high
values on one variable to be associated with low values on the other (e.g., as stress increases,
emotional well-being decreases); also called an inverse relationship.


network sampling

The sampling of participants based on referrals from others already in the
sample; also called snowball sampling.


nondirectional hypothesis

A research hypothesis that does not stipulate the expected direction of
the relationship between variables.


nonequivalent control group design

A quasi-experimental design involving a comparison group
that was not created through random assignment

nonexperimental research

Studies in which the researcher collects data without introducing an
intervention; also called observational research.


noninferiority trial

A trial designed to determine whether the effect of a new treatment is not
worse than a standard treatment by more than a pre-specified amount.

nonparametric tests

A class of statistical tests that do not involve stringent assumptions about the
distribution of critical variables.


nonprobability sampling

The selection of sampling units (e.g., participants) from a population
using nonrandom procedures (e.g., convenience and quota sampling).

nonresponse bias

A bias that can result when a nonrandom subset of people invited to participate
in a study fail to participate.

nonsignificant result

The result of a statistical test indicating that group differences or an observed
relationship could have occurred by chance, at a given level of significance; sometimes abbreviated as
NS.

normal distribution

A theoretical distribution that is bell-shaped and symmetrical; also called a
normal curve or a Gaussian distribution

null hypothesis

A hypothesis stating no relationship between the variables under study; used
primarily in statistical testing as the hypothesis to be rejected.


number needed to treat (NNT)

An estimate of how many people would need to receive an
intervention to prevent one undesirable outcome, computed by dividing 1 by the value of the
absolute risk reduction.

objectivity

The extent to which two independent researchers would arrive at similar judgments or
conclusions (i.e., judgments not biased by personal values or beliefs).


odds

A way of expressing the chance of an event—the probability of an event occurring to the
probability that it will not occur, calculated by dividing the number of people who experienced an
event by the number for whom it did not occur.


odds ratio (OR)

The ratio of one odds to another odds, for example, the ratio of the odds of an event
in one group to the odds of an event in another group; an odds ratio of one indicates no difference
between groups.

on-protocol analysis

A principle for analyzing data that includes data only from those members of a
treatment group who actually received the treatment.

one-tailed test

A statistical test in which only values in one tail of a distribution are considered in
determining significance; sometimes used when the researcher states a directional hypothesis.

open-ended question

A question in an interview or questionnaire that does not restrict
respondents’ answers to preestablished alternatives.


operationalization

The process of translating research concepts into measurable phenomena.


ordinal measurement

A measurement level that rank orders phenomena along some dimension.


outcome measure

A term sometimes used to refer to the dependent variable, that is, the measure
that captures the outcome of an intervention.


outcomes research

Research designed to document the effectiveness of health care services and the
end results of patient care.


outliers

Values that lie outside the normal range of values for other cases in a data set.


p value

In statistical testing, the probability that the obtained results are due to chance alone; the
probability of a Type I error.


parametric tests

A class of statistical tests that involve assumptions about the distribution of the
variables and the estimation of a parameter.

Pearson’s r

A correlation coefficient designating the magnitude of relationship between two
variables measured on at least an interval scale; also called the product-moment correlation.

peer reviewer

A researcher who reviews and critiques a research report or proposal, and who
makes a recommendation about publishing or funding the research.


permuted block randomization

Randomization that occurs for blocks of subjects of even size (e.g.,
6 or 8 at a time), to ensure that, at any given time, roughly equal numbers of subjects have been
allocated to all treatment groups.


pilot study

A small-scale version, or trial run, done in preparation for a major study (the parent
study).


placebo

A sham or pseudo intervention, often used as a control group condition.

placebo effect

Changes in the dependant variable attributable to the placebo condition.

point prevalence rate

The number of people with a condition or disease divided by the total
number at risk, multiplied by the total number for whom the rate is being established (e.g., per 1000
population).


population

The entire set of individuals or objects having some common characteristics (e.g., all RNs
in Canada); sometimes called universe.


positive predictive value (PPV)

A measure of the usefulness of a screening/diagnostic test that can
be interpreted as the probability that a positive test result is correct; calculated by dividing the
number with a positive test who have disease by the number with a positive test.


positive relationship

A relationship between two variables in which high values on one variable
tend to be associated with high values on the other (e.g., as physical activity increases, pulse rate
increases).


positive results

Research results that are consistent with the researcher’s hypotheses.

positively skewed distribution

An asymmetric distribution of values with a disproportionately
high number of cases at the lower end; when displayed graphically, the tail points to the right.

post hoc test

A test for comparing all possible pairs of groups following a significant test of overall
group differences (e.g., in an ANOVA).


posttest

The collection of data after introducing an intervention.

posttest-only design

An experimental design in which data are collected from subjects only after
the intervention has been introduced; also called an after-only design.

power

A research design’s ability to detect relationships that exist among variables.


power analysis


A procedure for estimating either the likelihood of committing a Type II error or
sample size requirements.

precision

In statistics, the extent to which random errors have been reduced, usually expressed in
terms of the width of the confidence interval around an estimate.


prediction

The use of empirical evidence to make forecasts about how variables will behave in a
new setting and with different individuals.

predictive validity

The degree to which an instrument can predict a criterion observed at a future
time.

pretest

(1) The collection of data prior to the experimental intervention; sometimes called baseline
data; (2) The trial administration of a newly developed instrument to identify flaws or assess time
requirements.

pretest-posttest design

An experimental design in which data are collected from research subjects
both before and after introducing an intervention; also called a before–after design.

prevalence study

A cross-sectional study undertaken to estimate the proportion of a population
having a particular condition (e.g., multiple sclerosis) at a given point in time.

probability sampling

The selection of sampling units (e.g., participants) from a population using
random procedures (e.g., simple random sampling, cluster sampling).


proposal

A document communicating a research problem, its significance, proposed procedures for
solving the problem, and, when funding is sought, how much the study will cost.

prospective design

A study design that begins with an examination of presumed causes (e.g.,
cigarette smoking) and then goes forward in time to observe presumed effects (e.g., lung cancer); also
called a cohort design.


psychometric assessment

An evaluation of the quality of an instrument, based primarily on
evidence of its reliability and validity

psychometrics

The theory underlying principles of measurement and the application of the theory
in the development of measuring tools.


purposive (purposeful) sampling

A nonprobability sampling method in which the researcher
selects participants based on personal judgment about which ones will be most informative; also
called judgmental sampling.


Q sort

A data collection method in which participants sort statements into a number of piles (usually
9 or 11) according to some bipolar dimension (e.g., most helpful/least helpful).


quantitative analysis

The manipulation of numeric data through statistical procedures for the
purpose of describing phenomena or assessing the magnitude and reliability of relationships among
them.

quantitative data

Information collected in a quantified (numeric) form.

quantitative research

The investigation of phenomena that lend themselves to precise
measurement and quantification, often involving a rigorous and controlled design.

quasi-experimental design

A design for an intervention study in which subjects are not randomly
assigned to treatment conditions; also called a nonrandomized trial or a controlled trial without
randomization.

questionnaire

A document used to gather self-report data via self-administration of questions.


quota sampling

A nonrandom sampling method in which “quotas” for certain sample characteristics
are established to increase the representativeness of the sample.

r

The symbol for a bivariate correlation coefficient, summarizing the magnitude and direction of a
relationship between two variables measured on an interval or ratio scale.

R

The symbol for the multiple correlation coefficient, indicating the magnitude (but not direction) of
the relationship between the dependent variable and multiple independent variables, taken together.

The squared multiple correlation coefficient, indicating the proportion of variance in the
dependent variable explained by a group of independent variables.


random assignment

The assignment of subjects to treatment conditions in a random manner (i.e.,
in a manner determined by chance alone); also called randomization.


random sampling

The selection of a sample such that each member of a population has an equal
probability of being included.


randomization

The assignment of subjects to treatment conditions in a random manner (i.e., in a
manner determined by chance alone); also called random assignment.


randomized clinical trial (RCT)

A full experimental test of an intervention, involving random
assignment to treatment groups; sometimes, phase III of a full clinical trial.


range

A measure of variability, computed by subtracting the lowest value from the highest value in a
distribution of scores.


rating scale

A scale that requires ratings of an object or concept along a continuum.


raw data

Data in the form in which they were collected, without being coded or analyzed.

receiver operating characteristic curve (ROC curve)

A method used in developing and refining a
screening instrument to determine the best cutoff point for “caseness.”

refereed journal

A journal in which decisions about the acceptance of manuscripts are made based
on recommendations from peer reviewers.


regression analysis

A statistical procedure for predicting values of a dependent variable based on
one or more independent variables.


relationship

A bond or a connection between two or more variables.


relative risk (RR)

An estimate of risk of “caseness” in one group compared to another, computed by
dividing the absolute risk for one group (e.g., an exposed group) by the absolute risk for another (e.g.,
the nonexposed); also called the risk ratio.


reliability

The degree of consistency or dependability with which an instrument measures an
attribute.

reliability coefficient

A quantitative index, usually ranging in value from .00 to 1.00, that provides
an estimate of how reliable an instrument is (e.g., Cronbach’s alpha).


repeated-measures ANOVA

An analysis of variance used when there are multiple measures of the
dependent variable over time (e.g., in a crossover design).


replication

The deliberate repetition of research procedures in a second investigation for the
purpose of determining if earlier results can be confirmed.


representative sample

A sample whose characteristics are comparable to those of the population
from which it is drawn.

research design

The overall plan for addressing a research question, including specifications for
enhancing the study’s integrity.

research hypothesis

The actual hypothesis a researcher wishes to test (as opposed to the null
hypothesis), stating the anticipated relationship between two or more variables.


research methods

The techniques used to structure a study and to gather and analyze information
in a systematic fashion.

research problem

An enigmatic or perplexing condition that can be investigated through
disciplined inquiry

research question

A statement of the specific query the researcher wants to answer to address a
research problem.

respondent

In a self-report study, the study participant responding to questions posed by the
researcher.


response rate

The rate of participation in a study, calculated by dividing the number of persons
participating by the number of persons sampled.


response set bias

The measurement error resulting from the tendency of some individuals to
respond to items in characteristic ways (e.g., always agreeing), independently of item content.


retrospective design

A study design that begins with the manifestation of the dependent variable in
the present (e.g., lung cancer), followed by a search for a presumed cause occurring in the past (e.g.,
cigarette smoking).

rival hypothesis

An alternative explanation, competing with the researcher’s hypothesis, for
interpreting the results of a study.


sample

A subset of a population, selected to participate in a study.


sampling

The process of selecting a portion of the population to represent the entire population.

sampling bias

Distortions that arise when a sample is not representative of the population from
which it was drawn.

sampling error

The fluctuation of the value of a statistic from one sample to another drawn from the
same population.

sampling frame

A list of all the elements in the population, from which the sample is drawn.


sampling plan

The formal plan specifying a sampling method, a sample size, and procedures for
recruiting subjects.

scale

A composite measure of an attribute, involving the combination of several items that have a
logical and empirical relationship to each other, resulting in the assignment of a score to place people
on a continuum with respect to the attribute

scatter plot

A graphic representation of the relationship between two variables.

screening instrument

An instrument used to determine whether potential subjects for a study meet
eligibility criteria, or for determining whether a person tests positive for a specified condition.


selection threat (self-selection)

A threat to the internal validity of the study resulting from
preexisting differences between groups under study; the differences affect the dependent variable in
ways extraneous to the effect of the independent variable.

self-report

A method of collecting data that involves a direct report of information by the person
who is being studied (e.g., by interview or questionnaire).


semantic differential

A technique used to measure attitudes in which respondents rate concepts of
interest on a series of bipolar rating scales.


semi-structured interview

An interview in which the researcher has a list of topics to cover rather
than specific questions to ask.

sensitivity

The ability of screening instruments to correctly identify a “case,” that is, to correctly
diagnose a condition

setting

The physical location and conditions in which data collection takes place in a study

significance level

The probability that an observed relationship could be caused by chance;
significance at the .05 level indicates the probability that a relationship of the observed magnitude
would be found by chance only 5 times out of 100.

simple random sampling

Basic probability sampling involving the selection of sample members
from a sampling frame through completely random procedures.

site

The overall location where a study is undertaken.

snowball sampling

The selection of participants through referrals from earlier participants; also
called network sampling.


social desirability response set

A bias in self-report instruments created when participants have a
tendency to misrepresent their opinions in the direction of answers consistent with prevailing social
norms.

Spearman’s rank-order correlation (Spearman’s rho)

A correlation coefficient indicating the
magnitude of a relationship between variables measured on the ordinal scale.


specificity

The ability of a screening instrument to correctly identify noncases.

standard deviation

The most frequently used statistic for measuring the degree of variability in a
set of scores.


standard scores

Scores expressed in terms of standard deviations from the mean, with raw scores
transformed to have a mean of zero and a standard deviation of one; also called z scores.

statistical power

The ability of the research design to detect true relationships among variables.


statistical significance

A term indicating that the results from an analysis of sample data are
unlikely to have been caused by chance, at a specified level of probability.

strata

Subdivisions of the population according to some characteristic (e.g., males and females);
singular is stratum.


stratified random sampling

The random selection of study participants from two or more strata of
the population independently.

subject

An individual who participates and provides data in a study; term used primarily in
quantitative research.

summated rating scale

See Likert scale.

symmetric distribution

A distribution of values with two halves that are mirror images of the each
other.


systematic sampling

The selection of sample members such that every kth (e.g., every tenth) person
or element in a sampling frame is chosen.


target population

The entire population in which a researcher is interested and to which he or she would like to generalize the study results.


test–retest reliability

Assessment of the stability of an instrument by correlating the scores obtained on two administrations.

time series design

A quasi-experimental design involving the collection of data over an extended
time period, with multiple data collection points both prior to and after an intervention.

treatment group

The group receiving the intervention being tested; the experimental group.

t-test

A parametric statistical test for analyzing the difference between two means.


Type I error

An error created by rejecting the null hypothesis when it is true (i.e., the researcher concludes that a relationship exists when in fact it does not—a false positive).


Type II error

An error created by accepting the null hypothesis when it is false (i.e., the researcher concludes that no relationship exists when in fact it does—a false negative).


two-tailed tests

Statistical tests in which both ends of the sampling distribution are used to determine improbable values.

univariate descriptive study

A study that gathers information on the occurrence, frequency of occurrence, or average value of the variables of interest, one variable at a time, without focusing on interrelationships among variables.


univariate statistics

Statistical analysis of a single variable for purposes of description (e.g., computing a mean).


validity

A quality criterion referring to the degree to which inferences made in a study are accurate
and well-founded; in measurement, the degree to which an instrument measures what it is intended to measure.


validity coefficient

An index, usually ranging from .00 to 1.00, yielding an estimate of how valid an
instrument is.

variability

The degree to which values on a set of scores are dispersed.

variable

An attribute that varies, that is, takes on different values (e.g., body temperature, heart
rate).


visual analog scale (VAS)

A scaling procedure used to measure certain clinical symptoms (e.g., pain, fatigue) by having people indicate on a straight line the intensity of the symptom.


Wilcoxon signed ranks test

A nonparametric statistical test for comparing two paired groups, based on the relative ranking of values between the pairs.


within-subjects design

A research design in which a single group of subjects is compared under different conditions or at different points in time (e.g., before and after surgery).