ABCDEFGHIJKLMNOPQRSTUVWXYZ
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Formula from Cohen 1984 (note typo on p. 250)
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SDs away from mean2
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h (Ordinate of normal curve)
0.05
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Expected proportion0.98
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e (reduction in effect)0.362
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Note: This calculates the expected reduction in the rxy correlation when one variabe is dichotomized at a given number of SDs away from its own mean
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Dichotimizing at the mean is 0 SDs away from it, with the least amount of reduction in the correlation. This results in a correlation that is 79.8% of the original in magnitude
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If SDs are not known (for example, one has results from a model using dichotomized variables but no access to the raw data) different SDs can be attempted
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until the reported proportion is achieved. This should be used with EXTREME caution.
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Key:
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Input
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Informative
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Output
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