<PRE><B>Question 507513</B>
Given the following frequency distribution, find the mean, variance, and standard deviation. Please show all of your work.
Errors Frequency
36-38 18
39-41 7
42-44 12
45-47 22
48-50 13 
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You have to use each class mark as the representative data value 
for each class:
1st class mark is (38+36)/2 = 37
Do the same for each class.
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Mean = [37*18+40*7+41*12+46*22+49*13]/[18+7+12+22+13] = 43
std = 4.7434
variance = 4.7434^2 = 22.4998
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Cheers,
Stan H.</PRE>