SOLUTION: Suppose that from the past experience a professor knows that the test score of a student taking his final examination is a random variable with mean 70 and standard deviation 11. H
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Question 1189545: Suppose that from the past experience a professor knows that the test score of a student taking his final examination is a random variable with mean 70 and standard deviation 11. How many students would have to take the examination to ensure, with probability at least 0.94, that the class average would be within 2.5 of 70? Answer by Boreal(15235) (Show Source):
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z(0.03)=-1.88
z(0.97)=+1.88
error=z*sd/sqrt(n)
error^2=z^2*sd^2/n
n=z^2*sd^2/error^2
=1.88^2*121/6.25
=68.43 or 69 students
