Interesting question. Glancing through a couple stats books it is occasionally mentioned as a method but quickly dismissed.
Welkowitz, Ewen & Cohen (1992; 4th ed.) notes that averaging the absolute values is a useful descriptive measure termed Average Deviation. They go on to say "it is usually rejected because absolute values are unsuitable for further statistical analysis." A stats for engineers book by Kennedy & Neville (1976; 2nd ed.) states "the usefulness of the mean deviation in statistical calculations is small, and practically no statistical methods of analysis involve its use." Another text (Howell1992; 3rd ed.) called it the M.A.D. (mean absolute deviation) and goes on to say "for all its simplicity and intuitive appeal, the mean absolute deviation has not played an important role in statistics. Instead, much more useful measures, the variance and the standard deviation, are normally used." Spence, Underwood, Duncan & Cotton (1968; 2nd ed.) "Yet, for various reasons, the average deviation is rarely used as a measure of variability." Levine's (1981) text offers the closest to a justification why it is not used. It states that it is useful but "... it is not useable in conjunction with most statistical techniques, which require consistence with the laws of algebra. Ignoring the signs of numbers violates the laws of algebra." Patrick (any excuse to not grade this afternoon...) ********************* Patrick O. Dolan Assistant Professor Department of Psychology Drew University Madison, NJ 07940 973-408-3558 [EMAIL PROTECTED] ********************* ----- Original Message ----- From: "Wallace E. Dixon, Jr." <[EMAIL PROTECTED]> To: "Teaching in the Psychological Sciences" <[EMAIL PROTECTED]> Sent: Tuesday, February 25, 2003 12:40 PM Subject: SD Woes > 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? > > wedj > > -- > -------------------------------------------------------------------- -------- > Wallace E. Dixon, Jr. | > Chair and Associate Professor | Rocket science is child's play > of Psychology | compared to understanding > Department of Psychology | child's play > East Tennessee State University | -unknown > Johnson City, TN 36714 | > (423) 439-6656 | > -------------------------------------------------------------------- -------- > > --- > You are currently subscribed to tips as: [EMAIL PROTECTED] > To unsubscribe send a blank email to [EMAIL PROTECTED] > > --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
