Hi;

I have two sets of data and need to find there combined standard deviation.

What I know 1: for a set of 10 numbers sum of x=50 and sum of x(squared)=310.

1: for a set of 15 numbers sum of x=86 and sum of x(squared)=568.

I know how to find the standard deviation ofthe individual sets but don't know how to

combine them.

Thanks.