Experiments and Observational Studies (Chapter 5)

Vocabulary flashcards covering key terms from Chapter 5 on experiments and observational studies.

Response variable (RESP)

The primary measurement of interest in a study; the outcome researchers compare across groups.

Explanatory variable (EXPL) / Factor

A variable about each subject that may explain differences in the RESP; often several EXPL are considered.

Treatment

The value of the EXPL that is deliberately set by the researcher in an experiment.

Experiment

A study in which the EXPL is controlled or manipulated by the researcher.

Observational study

A study in which the EXPL is determined by nature and not controlled by the researcher.

Confounding variable

A variable related to both the EXPL and the RESP, causing extraneous differences between groups.

Interacting variable / Interaction

A variable that changes the effect of the EXPL on the RESP; the effect depends on the value of another variable.

Placebo

A fake treatment that resembles the real treatment but has no active ingredient.

Placebo effect

The tendency of subjects to respond to any treatment, even if it is inactive.

Control group

A treatment group that receives essentially no experimental treatment.

Population of interest

The group about which researchers want to draw conclusions.

Retrospective study

A study in which subjects are asked to recall past events.

Prospective study

A study in which subjects are followed forward in time into the future.

Hawthorne Effect

The phenomenon where subjects alter their behavior because they know they are being observed.

Experimenter Effect

The tendency of researchers to see what they expect or want to see, biasing results.

Confounding variable example: severity of winter

An example where an extraneous factor (winter severity) could influence outcomes (colds) alongside the EXPL.

Interaction example: temperature and detergent

An example showing that the best detergent depends on water temperature; an interaction between factors.