Posted by Jennifer on Thursday, November 10, 2011 at 7:39pm.
Given the following frequency distribution, find the mean, variance, and standard deviation.
Class Frequency
3133 18
3436 25
3739 22
4042 9
4345 20

Math  PsyDAG, Friday, November 11, 2011 at 11:07am
Find the mean first = sum of scores/number of scores (Use midpoint of classes as the values of the scores.)
Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.
Standard deviation = square root of variance
I'll let you do the calculations.