between ordinal data and other categorical variables, normally in a contingency tables. A correlation r is found between the variables where r lies between -1 and 1. To test the trend, a test statistic:
: is used where n is the sample size.

R can be found by letting be the row scores and be the column scores. Let be the mean of the row scores while . Then is the marginal row probability and is the marginal column probability. R is calculated by: