Operational Definitions

operational definition

a statement of the procedures used to define research variables

Hypothesis

A testable prediction, often implied by a theory

independent variable

The experimental factor that is manipulated; the variable whose effect is being studied.

dependent variable

The outcome factor; the variable that may change in response to manipulations of the independent variable.

random sample

a sample that fairly represents a population because each member has an equal chance of inclusion

sampling bias

a flawed sampling process that produces an unrepresentative sample

Random assignment

assigning participants to experimental and control conditions by chance, thus minimizing preexisting differences between those assigned to the different groups

correlation coefficient

a statistical index of the relationship between two things (from -1 to +1)

standard deviation

a computed measure of how much scores vary around the mean score

double-blind procedure

an experimental procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evaluation studies.

internal validity

extent to which we can draw cause-and-effect inferences from a study

control group

In an experiment, the group that is not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

observational study

observes individuals and measures variables of interest but does not attempt to influence the responses