SOLUTION: The following is a summary of test grades for a class. Estimate the population mean and standard deviation. (Round answers to 2 decimals) Grades Frequency 91-100 3 81-

Question 1102937: The following is a summary of test grades for a class. Estimate the population mean and standard deviation. (Round answers to 2 decimals)

Grades Frequency
91-100 3
81-90 4
71-80 8
61-70 4
51-60 3

Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Find the center point for each bin, as an example,

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To find the mean, find the weighted average,

You could have also used a symmetry argument since the data values are centered about 75.5.
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Now for the standard deviation, sum the deviations from the mean, weight them, and take the square root.

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