Calculation for the test of the difference between two independent correlation coefficients
Kristopher J. Preacher (Vanderbilt University)
This web utility may be cited in APA style in the following manner:
Preacher, K. J. (2002, May). Calculation for the test of the difference between two independent correlation coefficients [Computer software]. Available from http://quantpsy.org.
This interactive calculator yields the result of a test of the hypothesis that two correlation coefficients obtained from independent samples are equal. The result is a z-score which may be compared in a 1-tailed or 2-tailed fashion to the unit normal distribution. By convention, values greater than |1.96| are considered significant if a 2-tailed test is performed.
First, each correlation coefficient is converted into a z-score using Fisher's r-to-z transformation. Then, making use of the sample size employed to obtain each coefficient, these z-scores are compared using formula 2.8.5 from Cohen and Cohen (1983, p. 54).
Enter the two correlation coefficients, with their respective sample sizes, into the boxes below. Then click on "calculate." The p-values associated with both a 1-tailed and 2-tailed test will be displayed in the "p" boxes.
Cohen, J., & Cohen, P. (1983). Applied multiple regression/correlation analysis for the behavioral sciences. Hillsdale, NJ: Erlbaum.