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 415 and 417 minutes during a particular month. Based on the information provided, what proportion of the company's customers would be eligible for the drawing?

Explanation / Answer

P(415 < x < 417) = P(((415 - 445.5) / 177.8) < z < ((417 - 445.5) / 177.8))

= P(-0.1715 < z < -0.1603)

= 0.4363 - 0.4319

= 0.0044

The correct answer is A. About 0.004

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