SOLUTION: A class has an equal number of boys and girls. The boys all got 85% on a test and the girls all got 91%. What are the mean and standard deviation of the test scores for the entire

Question 1022940: A class has an equal number of boys and girls. The boys all got 85% on a test and the girls all got 91%. What are the mean and standard deviation of the test scores for the entire class?
Answer by robertb(5830) (Show Source): You can put this solution on YOUR website!
We treat the entire class as a population.
Let n = number of boys = number of girls ==> total number of students is 2n.
==> The mean of the test scores would be , or %.
To find the standard deviation, use the formula for the population variance.
==>
==>
==> , to three decimal places.
The standard deviation is .
(Note that both averages of 85% and 91% are exactly one standard deviation from the mean!)
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