KR-20 =N /(N -1)[1 – Sum(p q)/Var(X)]
Where sum (p q) = sum of the product of the probability of responses; and to calculate coefficient alpha:
a =N/(N -1)[1 –sum Var(Y)/Var(X)]
where N = # items
sum Var (Y)= sum of item variances
Var(X) = composite variance (Allan &Yen, 1979)
Yes, l know, that’s why computers were invented