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 $29.54 per access line per month, with a standard deviation of $2.55. Company N's operating expenses were $34.70 per access line per month in the first half of 1994. Estimate the percentage of regional phone companies whose operating expenses were higher than those of Company N. ______________ %

Explanation / Answer

from normal distribution z=(X-mean)/std deviation

P(X>34.70)=1-P(Z<(34.70-29.54)/2.55)=1-P(Z<2.0235)=1-0.9785 =0.0215 ~2.15%

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