Qualitative personality usually consists of passive observations with no intent to manipulate the casual variable. On occasion, however, qualitative designs can take the form of natural experiments.

For example, When Prophecy Fails resembles an interrupted time series quasi experiment. Consider the experience of disconfirmation of belief as the independent variable. The believes encountered three such disconfirmations, in a period of four days. The disconfirmations (Xs) occurred at 4 P.M. (X,) and midnight (X2) of December 17 and at midnight of December 20 (X3).