# Determining the probability using mean and standard deviation.

A sample of 100 is taken from a population which has a normal distribution with a mean of 80 and a standard deviation of 40.

What is the probability that the sample mean is between 74 and 81 is?

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...81) = ?

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<br>Xbar - Normal (mean=80, sd=40/sqrt100 = 40/10 = 4)

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<br>P (74< Xbar < 81) ...