Research Methods and Statistics

A design with random assignment of participants to conditions and manipulation of an independent variable, allowing causal inferences.

A quasi-experiment manipulates an independent variable but lacks random assignment, often using preexisting groups, which weakens causal claims.

It can establish the degree and direction of association between variables but cannot establish causation because variables are not manipulated.

An intensive, in-depth examination of a single individual, group, or event, useful for rare phenomena and hypothesis generation but low in generalizability.

The extent to which a study supports the conclusion that the independent variable caused changes in the dependent variable, free of confounds.

The extent to which study results generalize to other populations, settings, times, and measures.