Suppose that the diameters of oak trees are normally distributed with a mean of 4 feet and a standard deviation of 0.375 feet. What is the probability of a sampling a set of 87 oaks trees and finding their mean to differ from the population mean by less than 0.1 feet in diameter?
Solution :
Given that,
mean = = 4
standard deviation = = 0.375
= / n = 0.375 / 87 = 0.0402
= P[(-0.1) / 0.0402< ( - ) / < (0.1) / 0.0402)]
= P(-2.49 < Z < 2.49)
= P(Z < 2.49) - P(Z < -2.49)
= 0.9936 - 0.0064
= 0.9872
Probability = 0.9872
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