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Item Variances and Median Splits: Some Discouraging and Disquieting Findings
Author(s) -
Bissonnette Victor,
Ickes William,
Bernstein Ira,
Knowles Eric
Publication year - 1990
Publication title -
journal of personality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.082
H-Index - 144
eISSN - 1467-6494
pISSN - 0022-3506
DOI - 10.1111/j.1467-6494.1990.tb00245.x
Subject(s) - trait , psychology , personality , variance (accounting) , artifact (error) , statistics , preference , reliability (semiconductor) , range (aeronautics) , big five personality traits , social psychology , econometrics , clinical psychology , mathematics , computer science , power (physics) , physics , quantum mechanics , neuroscience , programming language , materials science , accounting , business , composite material
In his response to our article, Baumeister argued that in real data, the confound between interitem variance and trait extremity is small (typically in the range of 0 and –.2), and that the danger of artifact associated with the application of median splits to interitem variance is not as serious as our first simulation study would lead one to believe. When we examined a large body of actual personality data, employing personality scales of average reliability and relatively large samples, we found that the average magnitude of the confound was –.15. However, we also found that even a confound as small as –.03 could be associated with significant differential range restriction of the trait scores within subsamples produced by the median split (MS) technique. We note that several factors, not just the magnitude of the interitem variance/trait extremity confound, must be considered when assessing the danger of artifact associated with the MS technique. We again conclude that researchers should use the moderated multiple regression (MMR) technique in preference to the MS technique when testing for moderating effects in personality research.