Selecting Statistics

Statistical Test

Biserial r

Statistical Measure

Refer critical ratio for biserial r to a table of the unit normal curve

Notes

This measure depends on a strict assumption of the normality of the continuous variables that have been dichotomized. Furthermore, the sampling error is large when dichotomies are extreme. Nunnally (1978, pages 135-137) advises against the use of these coefficients.

Biserial r: McNemar, Q. Psychological Statistics. Fourth edition. New York: Wiley 1969. p. 215; Nunnally, J. C. Psychometric Theory. Second edition. New York: McGraw-Hill, 1978. p. 135

Critical ratio test: McNemar, Q. Psychological Statistics. Fourth edition. New York: Wiley 1969. p. 217