Wednesday
October 22, 2014

Homework Help: Stats

Posted by Andrea on Wednesday, May 28, 2008 at 8:49pm.

a teacher teaches two sections (A and B) of a class. Both sections have a mean score of 75. Section A only has 5 students and they all received a score of 75, while section B has 15 students with a mean score of 75 with a variance of 12. What is the standard deviation of the combined class (N=20, treat as the population).
a)9 b)6 c)4 d)3 e)2

So as a result section A has zero for the variance. I am having trouble figuring out the correct equation to solve this problem.

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