This exercise uses the normal probability density function and requires the use

Question

This exercise uses the normal probability density function and requires the use of either technology or a table of values of the standard normal distribution. The cash operating expenses of the regional phone companies during the first half of 1994 were distributed about a mean of $29.79 per access line per month, with a standard deviation of $2.75. Company A's operating expenses were $27.00 per access line per month. Assuming a normal distribution of operating expenses, estimate the percentage of regional phone companies whose operating expenses were closer to the mean than the operating expenses of Company A were to the mean _____________ %

Explanation / Answer

here we need to find out % of companies whose expense is greater then (27+29.79)/2=28.395

P(X>28.395)=1-P(Z<(28.395-29.79)/2.75)=1-P(Z<-0.5073)=1-0.3060 =0.6940

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