The sample size is very simply the size of the sample. If there is only one sample, the letter "N" is used to designate the sample size. If samples are taken from each of "a" populations, then the small letter "n" is used to designate size of the sample from each population. When there are samples from more than one population, N is used to indicate the total number of subjects sampled and is equal to (a)(n). If the sample sizes from the various populations are different, then n

When correlations are computed, the sample size (N) refers to the number of subjects and thus the number of pairs of scores rather than to the total number of scores.

The symbol N also refers to the number of subjects in the formulas for testing differences between dependent means. Again, it is the number of subjects, not the number of scores.