I am giving the formula for the Combined Variance. Once you find this, the combined standard deviation is only a single step away...
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
I now now why me book says 3.25 they have just added the two standard deviations
which I can kind of see why this is wrong.
Can someone please give me the right answer so that I know for myself,
from the formula provided by Sambit I get a combined standard deviation of 5.5876 is this correct?
Please pop over to the calculator forum and help me out with putting two groups of frequency data in
and getting the combined standard deviation out.