Finding a population standard deviation given the SDs of 2 groups? Standard deviation problem here?

Question

Okay guys. I am given the sample standard deviation of 2 groups of exam results, i know the mean, range & median.

Using the numbers that i have, what is the procedure for calculating the Population Standard deviation of the entire group of results?

The entire group refers to combining the 1st 2 sections together to form a larger group.

Pls help, i dont get the calculations. If you need me to provide the actual paper, pls email me.

Answer 1

indeterminate solution. cannot determine or estimate a population standard deviation from "SDs of 2 groups".   One SD can be utilized as an "unbiased" estimator of population standard deviation accordingly:

SD (sample) = [standard deviation (population)] / sqrt(sample size)