.png){kind=icon}
Loss of subjects varies across experimental conditions.
This design eliminates the possibility of testing-X interaction.
A threat to internal validity when a single group is measured at two or more points in time.
May occur when measurement of the dependent variable varies over time or experimental conditions.
An experiment in which two or more variables are manipulated.
Selection and differential attribution are the primary threats to internal validity of this design.
A matter of how well an experiment controls for the effects of extraneous variables.
Resembles the one-group pretest-posttest design except multiple observations are made before and after the treatment.
The effect of X on Y depends on Z.
A potential threat to validity when subjects are selected on the basis of their extreme scores on the dependent variable.
May be confounded with the independent variable when a single group is studied over an extended period of time.
Pretests and posttests are administered to experimental conditions but random assignment is not possible.