Friday

February 27, 2015

February 27, 2015

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

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.

- Stats -
**PsyDAG**, Thursday, May 29, 2008 at 11:01amVariance = Σx^2/N, where x = X-μ. Since Σx^2 = 0 for the first group, it will contribute nothing to the Σx^2, so that term will remain the same for the combined class, but the N will increase from 15 to 20.

For the second group, since Variance = Σx^2/N,

Σx^2 = Variance * N = 12 * 15 = 180

Thus for the second group, variance = 180/20 = 9

However, the standard deviation is the square root of the variance. You should be able to calculate that.

I hope this helps. Thanks for asking.

**Answer this Question**

**Related Questions**

Statistics - A class has 3 sections. Here is a summary of the scores on the ...

stats - 2. A standardized exam was provided to all 3rd graders in Arizona ...

basic statistics for the behavioral sciences - there are 80 students enrolled in...

Math for the middle school and elementary teacher - A prof. teaches 2 calc. ...

Statistics - Students were given an exam with 300 multiple-choice questions. The...

math - students of class XI of a school were motivated to apply for NCC. from ...

Stats: need help please - two golfers plan to enter a tournament where the score...

Stats - A group of 56 randomly selected students have a mean score of 30.8 and a...

statistics - every year thousands of students take the SAT'S. Recent trends show...

math - Students were given an exam with 300 multiple-choice questions. The ...