In General, the Methods Used to Select Subjects Must Meet

In general, the methods used to select subjects must meet the scientific norm of generalizability. The researcher should be able to generalize from the sample to the population. Additionally, the cardinal rule of subject selection and experimentation is the comparability of the experimental and control groups. For results to be valid it is essential that he experimental and control groups be as _____ as possible.

A) different
B) dissimilar
C) incomparable
D) comparable