Beta Equation (Mutual Funds)

Beta Equation (Mutual Funds)
The calculation of beta in mutual funds is done as follows:
[(n) (sum of (xy)) ]-[ (sum of x) (sum of y)]
[(n) (sum of (xx)) ]-[ (sum of x) (sum of x)]
Here : n = # of observations (36 months)
x = return rate on the S&P 500 Index
y = return rate for the fund