Answer:
The formula for the point biserial correlation coefficient is:
point biserial correlation formula
M1 = mean (for the entire test) of the group that received the positive binary variable (i.e. the “1”).
M0 = mean (for the entire test) of the group that received the negative binary variable (i.e. the “0”).
Sn = standard deviation for the entire test.
p = Proportion of cases in the “0” group.
q = Proportion of cases in the “1” group.
Most people won’t work this formula by hand as most statistical software packages can calculate the coefficient for you.
