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 $29.76 per access line per month, with a standard deviation of $2.65. Company A's operating expenses were $29.00 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. (Round your answer to two decimal places.) %

Explanation / Answer

Mean of regional phone companies = 29.76

SD = 2.65

Company A's expenses = $29

We have to find:

P(29 < X < 29.76)

z1 = (29 - 29.76)/2.65 = - 0.29

z2 = 0

P(- 0.29 < z < 0) = 0.1141

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