Karl, Are you thinking about the "Kelly split?" In doing item analysis, Kelly recommended using the bottom 27% and top 27% of the cases. This simplified the computation (by hand) without sacrificing very much information. I think that the original reference might have been in the 1930s...
Bill __________________________________________________________________________ William B. Ware, Professor Educational Psychology, CB# 3500 Measurement, and Evaluation University of North Carolina PHONE (919)-962-7848 Chapel Hill, NC 27599-3500 FAX: (919)-962-1533 http://www.unc.edu/~wbware/ EMAIL: [EMAIL PROTECTED] __________________________________________________________________________ On Fri, 31 Jan 2003, Wuensch, Karl L wrote: > When interested in the relationship between two continuous > variables, some researchers will dichotomize one of them prior to analysis. > I generally discourage such dichotomization, but the practice is common. A > colleague asked me today about the practice of dichotomizing by a median > split (top half versus bottom half) versus the practice of using only the > tails (bottom third versus top third, for example). I outlined my thoughts > on this matter and noted that I vaguely recall having read an article or two > on this matter long ago, but cannot put my finger on the article(s). Can > any of you all? > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Karl L. Wuensch, Department of Psychology, > East Carolina University, Greenville NC 27858-4353 > Voice: 252-328-4102 Fax: 252-328-6283 > mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > http://core.ecu.edu/psyc/wuenschk/klw.htm > <http://core.ecu.edu/psyc/wuenschk/klw.htm> > > . > . > ================================================================= > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at: > . http://jse.stat.ncsu.edu/ . > ================================================================= > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
