In a lengthy list of measures (which are all in the same units), I am reporting both the Mean and the Median because some of the measures have a skewed distribution and others do not (I might also list the skewness and kurtosis, but that may be overkill). To index the dispersion of each measure, I am including the Standard Deviation (which seems most relevant in relation to the Mean) but am wondering what is best to use in relation to the Median.
Some articles report the Minimum and Maximum values of measures. This has the advantage of having the same meaning for all measures regardless of whether they are normally distributed or not. It has the disadvantage of being overly sensitive to extreme outliers, and therefore not being a very good index of the overall central tendency of the distribution -- making it less useful for comparing different measures to one another. At the opposite extreme, some articles list the inter-quartile range (values at the 25th and 75th percentile). This has the advantage of not being influenced by outliers and that it is easy to interpret (the middle 50% of the sample). However, it has the disadvantage of being narrower than the range defined by +/- 1 SD (the middle 68% of the sample) -- making it hard to compare the dispersion of different measures. Do people sometimes report the Median with the 16th and 84th percentile (the middle 68% of the sample)? If so, what is it called? This range would appear to have the advantage of being directly comparable to the breadth of the Mean +/- 1 SD. It seems logical to me, but I have never seen it. Perhaps there are other indices of central tendency that work equally well for the Mean and the Median? What would people recommend? Thanks! -- ************************************************* John H. Poole, Ph.D. Department of Psychiatry University of California Medical Center 4150 Clement Street (116C) San Francisco, CA 94061, USA Phone: 650-281-8851 Fax: 415-750-6996 Email: [EMAIL PROTECTED]; [EMAIL PROTECTED] ************************************************* . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
