A major cell phone service provider has determined that the number of minutes th

Question

A major cell phone service provider has determined that the number of minutes that its customers use their phone per month is normally distributed with a mean equal to 445.5 minutes with a standard deviation equal to 177.8 minutes. As a promotion, the company plans to hold a drawing to give away one free vacation to Hawaii for a customer who uses between 400 and 405 minutes during a particular month. Based on the information provided, what proportion of the company's customers would be eligible for the drawing?

A. About 0.01

B. About 0.004

C. Approximately 0.1026

D. Approximately 0.19

Explanation / Answer

mean = 445.5 and std. dev. = 177.8

P(400<X<405) = P((400-445.5)/177.8 < z < (405-445.5)/177.8) = P(-0.2559 < z < -0.2278) = 0.0109

Hence around 0.0109 proportion of the company's customers would be eligible for the drawing.

Hence Option (A)

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