A SIMPLE METHOD OF CALCULATING THE COEFFICIENT OF CORRELATION

• Published in: Journal of educational measurement Vol. 8; no. 3; pp. 221 - 222
• Main Author: WOLFE, JACK M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-09-1971; National Council on Measurement in Education
• Subjects: Arithmetic mean; Coefficients; Correlation coefficients; Correlations
• ISSN: 0022-0655; 1745-3984
• DOI: 10.1111/j.1745-3984.1971.tb00929.x

Where two sets of measurements can each be grouped into below average, average and above average classifications with an equal number assigned to each of the below average and above average classifications, a 3 by 3 table can then be tabulated with frequency counts. The exact value of the product moment coefficient of correlation can then be calculated very simply by means of the formula, r = (DIFF)/2m, where DIFF is the difference between the sum of the corner numbers on the positive diagonal and the sum of the corner numbers on the negative diagonal, and m equals the number in each of the below average and above average classifications for each variable. The formula for r is applicable to negative as well as positive correlation.