ABSTRACT
The above defining formula can be converted into a formula that is easier for computing purposes. Notice in the defining formula (16-1) that the averages of x and y need to be computed and then subtracted from each value of xi and yi. This
n - 1 Σ (xi - X¯ ) (yi -Y¯ )
n(Σ xi yi ) - (Σ xi)(Σyi ) n(n - 1)
4(83) - (10)(29
) 4(4 - 1)
means that all the values of xi and yi must be stored in memory somewhere. Also, if the values of X and Y are not rounded properly or have repeating decimals that round poorly, the results of the calculations using Equation 16-1 could be in error. Therefore, the following formula, which is mathematically equivalent to 16-1, is a more accurate method to obtain the same results.
