Solved Example on Probable Error

Example: If the value of coefficient of correlation between two series is +.9 and its probable error is .0128, what would be the value of n?

Solution: P.E. (r) = .6745 (1-r2)/√n from the given data

0.0128 = .6745 (1-(.9)2)/√n

0.0128 = (.6745×(1 - .81))/√n=(.128155)/√3
.0128 = (.128155)/√n
.0128 = .128155 or √n = (.128155)/0.128 = 10
n = (10)2 = 100