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 $29.98 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.)

Answer 1

Solution Given that mean H 29'98 standodd deviation o : 2.65 Company A's opedating cxpnses : 29.00 29 98-29 = a.98 29.98+0.98 - 30.96 PCx<A)= P -mean/standodd deviation) P(degional phone companies whose opedating the than the Ccpenses aede close to mean opedating expernses of company A ate wede to the mean P(29x306) PCx<30.96) P(x< 29) 30 96-29.98 29-29.98 2 65 2.65 0.98 0.98 2 65 2.65 9P(2<o3e98)- Pz<-0-3698) F'o 6412- o 3558 288 28.84 Thus, The pescerctage is