Hi On Tue, 25 Feb 2003, Wallace E. Dixon, Jr. wrote:
> Speaking of z-score woes, does anyone know how psychology ended up > with standard deviations rather than mean absolute differences from > the mean. Is it just because of ease of calculation? It is because of the statistical properties associated with the SD and the closely linked Mean, as determined by statisticians rather than psychologists. For example, the M is the center of a distribution in the sense that the sum of squared deviations about the mean (SS) is a minimum. SS, of course, is the basis for the variance and SD. The appropriate measure of central tendency for absolute differences is the median not the mean. Numerous other statistical properties hinge on the SD (or its close relatives SS or variance), including the z-scores discussed here of late. Just consider the t-test, the F-test, R^2, ... Best wishes Jim ============================================================================ James M. Clark (204) 786-9757 Department of Psychology (204) 774-4134 Fax University of Winnipeg 4L05D Winnipeg, Manitoba R3B 2E9 [EMAIL PROTECTED] CANADA http://www.uwinnipeg.ca/~clark ============================================================================ --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
