PSY 3314 Experimental Psychology Flashcards

Flashcards for vocabulary review.

Single-case experiment designs

Experimental designs that allow conclusions based on data from one or very few research participants.

Reversal design

A single-case design in which the treatment is introduced and then withdrawn during a second baseline period.

Multiple baseline design

Observing behavior before and after a manipulation under multiple circumstances.

Quasi-experimental designs

Approximate the control features of true experiments to infer that a given treatment did have its intended effect.

One-group posttest-only design

A quasi-experimental design that has no control group and no pretest comparison; a very poor design in terms of internal validity.

One-group pretest-posttest design

Obtains a comparison by measuring participants before and after a manipulation.

History effects

Events that occur during the course of the experiment that could be responsible for the results.

Maturation

Any naturally occurring change within the individual that is responsible for the results.

Testing effect

Simply taking the pretest changes the participant’s behavior.

Instrument decay

Change in the basic characteristics of the measuring instrument over time that could be responsible for the results.

Regression toward the mean

The principle that extreme scores on a variable tend to be closer to the mean when a second measurement is made.

Nonequivalent control group design

Compares an experimental group with a separate control group, but the two groups are not equivalent.

Selection differences/selection bias

Differences become a confounding variable, a problem.

Nonequivalent control group pretest-posttest design

Compares an experimental group with a nonequivalent control group, but also includes a pretest to assess initial differences.

Propensity score matching

A method of equating groups in quasi-experimental designs by matching individuals on a propensity score, which estimates the probability of assignment to a treatment and control condition based on a combination of scores on several variables.

Interrupted time series design

Examines the dependent variable over an extended period of time, both before and after the independent variable is implemented.

Control series design

An extension of the interrupted time series design in which there is a comparison or control group.

Cross-sectional method

Persons of different ages are measured at only one point in time.

Longitudinal method

The same group of people is observed at different times as they grow older.

Sequential method

A combination of the longitudinal and cross-sectional methods.

Cohort

A group of people born at about the same time and exposed to the same societal events; cohort effects are differences among age groups attributed to social, cultural, economic, or political differences rather than to the effect of age.

Cohort effects

Differences among age groups attributed to social, cultural, economic, or political differences rather than to the effect of age.

Nominal scale

The levels of variables have no numerical or quantitative properties.

Ordinal scale

Measurement categories form a rank order sequence.

Interval scale

Allows for more sophisticated statistical treatments; the intervals between the numbers on the scale are equal in size.

Ratio scale

Has an absolute zero point that indicates the absence of the variable being measured.

Three basic ways of describing the results of a study

Comparing group percentages, correlating scores, and comparing group means.

Frequency distribution

An arrangement of a set of scores from lowest to highest that indicates the number of times each score was obtained.

Central tendency

A single number or value that describes the typical or central score among distribution.

Mean (M)

Obtained by adding all the scores and dividing by the number of scores.

Median (Mdn)

The score that divides the group in half (with 50% scoring below and 50% scoring above).

Mode

The most frequent score.

Variability

The amount of spread in a distribution of scores.

Standard deviation (s or SD)

Indicates the average deviation of scores from the mean.

Variance

The square of the standard deviation; symbolized as s².

Range

The difference between the highest score and the lowest score.

Correlation coefficient

A statistic that describes how strongly variables are related to one another.

Pearson product–moment correlation coefficient

Used when both variables have interval or ratio scale properties; called the Pearson r.

Scatterplot

A graph of data in which the scores on one variable are plotted on the x-axis and the scores on the other variable are plotted on the y-axis; each point represents a single participant.

Restriction of range

A problem when scores on a variable are limited to a small subset of their possible values, making it more difficult to identify relationships of the variable to other variables of interest.

Effect size

An index of the magnitude or strength of an effect.

Regression equations

Calculations used to predict a person’s score on one variable when that person’s score on another variable is already known.

Multiple regression

Used to analyze the relationship between a single criterion variable and more than one predictor variable.

Multiple correlation

The correlation between a combined set of predictor variables and a single criterion variable.

Mediating variable

Hypothesized to be intervening between variable X and variable Y. Variable X affects the mediating variable first.

Moderating variable

Influences the relationship between variable X and variable Y.

Structural equation modeling (SEM)

Statistical techniques to evaluate a model that specifies a set of relationships among a set of variables.

Inferential statistics

Are used to draw conclusions about the population from sample data.

Null hypothesis

The population means are equal; the independent variable has no effect.

Research hypothesis

The population means are, in fact, not equal; the independent variable did have an effect.

Probability

The likelihood of the occurrence of some event or outcome.

Alpha level

The probability required for significance.

T-test

Commonly used to examine whether two groups are significantly different from one another.

One-tailed tests

The research hypothesis specifies a direction of difference between the groups.

Two-tailed tests

The research hypothesis does not specify the direction of difference.

Analysis of variance/F test

A more general statistical procedure than the t test; used when there are more than two levels of an independent variable and when a factorial design with two or more independent variables has been used.

Systematic variance

The deviation of the group means from the grand mean, or mean score of all individuals in all groups.

Error variance

The deviation of the individual scores in each group from their respective group means.

Confidence interval

An interval of values within which there is a given level of confidence (e.g., 95%) where the population value lies.

Type I error

Is made when we reject the null hypothesis, but the null hypothesis is true in the population.

Type II error

Occurs when the null hypothesis is accepted but the research hypothesis is true in the population; that is, a real effect exists, but the results of the experiment do not lead to a decision to reject the null hypothesis.

Power of a statistical test

The probability that the test will correctly reject a false null hypothesis.