Question 481825
Given the following frequency distribution, find the mean, variance, and standard deviation.  Please show all of your work.
 

Errors    Frequency
76-78         12
79-81         25
82-84         6
85-87         25
88-90         10

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The class mark represents the class value and 
is the average of the class limits.
1st: 77 
2nd: 80
3rd: 83
4th: 86
5th: 89
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Multiply each class mark by the class frequency
and add those products
Divide by the total of the frequencies to get the mean = 82.85
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I used a calculator to get the standard deviation = 4.01
The variance is the square of the standev = 4.01^2 = 16.11
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Cheers,
Stan H.
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