The . . . . . . . . , though difficult to calculate, is the best measure of dispersion since it takes into consideration the whole data and the deviations are taken from the arithmetic mean.

A. Raw data B. Ungrouped data C. Either A or B D. None of the above

A. Geometric mean B. Arithmetic mean C. Median D. None of the above

A. Parallel-forms reliability B. Equivalent forms reliability C. Comparable forms reliability D. All of the above

A. Case histories B. Tests C. Surveys D. None of the above