Question

14. + 0/6.66 points Previous Answers My Notes 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 $29.9 per access line per month, with a standard deviation of $2.55. 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. (Round your answer to two decimal places.) X % Enter a number. Submit Answer Practice Another Version

Answer 1

Solution :

Given that ,

mean = $\mu$ = 29.9

standard deviation = $\sigma$ = 2.55

P(x < 27.00) = P[(x - $\mu$ ) / $\sigma$ < (27.00 - 29.9) / 2.55]

= P(z < -1.14)

Using z table,

= 0.1271

The percentage is = 12.71%