Biserial Correlation Coefficient

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Description | Example | Discussion | See also

Description

The Biserial Correlation Coefficient is used where there are two sets of scores for the same people or for two matched groups.

It is calculated as:

R_b = ( (M1 - M2) * p₁p₂ ) / ZS_y

where M₁ and M₂ are the means of the two groups. p₁ and p₂ are the proportions of the two groups form of the total. Sy is the standard deviation on the continuous variable as a whole and Z is the Z-score from a table of the normal distributions for p₁ or p₂, whichever is smaller.

Discussion

This coefficient should not be used if p₁ or p₂ is larger than 0.9 (and is shaky if close to this).