Research terms and definitions

Analysis of Covariance (ANCOVA)
A statistical procedure used to test mean differences among groups on a dependent variable, while controlling for one or more extraneous variables.

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.

Between Subjects Design
A research design in which there are separate groups of people being compared (smoker vs nonsmoker).

Case-control Design
A nonexperiemental research design involving the comparison of a case and a matched control.

Confidence Level
The estimated probability that a population parameter lies within a given confidence interval.

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.

Crossover Design
An experimental design in which one group of subjects is exposed to more thann one condition or treatment in random order; sometimes called a repeated measures design.

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 development groups.

Deductive Reasoning
The process of developing specific predictions from general populations.

Dependent Variable
The variable hypothesized to depend on or be caused by another variable.

Double-Blind Experiment
An experiment in which neither the subjects not those who administer the treatment know who is in the experimental or control group.

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

Factorial Design
An experimental design in which two or more independent variable are simultaneously manipulated, permitting a separate analysis of the main effects of the independent variables, plus the interaction effects of those variables.

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 finds can be generalized from the sample to the population.

Independent Variable
The variable that is believed to cause or influence the dependent variable; in experimental research, the manipulated variable.

Inductive Reasoning
The process of reasoning from specific observations to more general rules.

Internal Validity
The degree to which it can be inferred that the experimental treatment, rather than uncontrolled, extraneous factors, is responsible for observed effects.

A technique for quantitatively combining and thus integrating the results of multiple studies on a given topic.

Null hypothesis
A hypothesis stating no relationship between variables under study.

Observational Research
Studies in which data are collected by observing and recording behaviors or activities relating to a phenomenon of interest.

Prospective Design
A study design that begins with an examination of presumed causes and then goes forward in time to observe presumed effects.

Qualitative Analysis
The organization and interpretation of nonnumeric data for the purpose of discovering important underlying dimensions and patterns of relationships.

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.

An intervention study in which subjects are not randomly assigned to treatment conditions, but the researcher exercises certain controls to enhance the study’s internal validity.

The assignment of subjects to treatment conditions in a random manner.

The degree of consistency or dependability with which an instrument memasures the attribute it is designed to measure.

Research Hypothesis
The actual hypothesis a researcher wishes to test, stating the anticipated relationship between two or more variables.

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

Retrospective Design
A study design that begins with the manifestation of the dependent variable in the present and searches for the presumed cause occurring in the past.

The ability of screening instruments to correctly identify a case.

The extent to which findings can be transferred to other settings or groups.

The degree to which an instrument measures what it is intended to measure.