Question

1. (a) The time needed to complete a final examination in a particular college course is normally distribution with a mean of 80 minutes and a standard deviation of 10 minutes. What is the probability that a student will complete the exam between 60 and 100 minutes?

1 (b) The mean preparation fee H&R Block charged retail customers last year was $183. Use this price as the population mean and assume the population standard deviation of preparation fees is $50. What is the probability that the mean price for a sample of 50 H&R Block retail customers is within $8 of the population mean?

Answer 1

1.

a)

μ=80, σ=10

We need to compute Pr(60≤X≤100).

The corresponding z-values =

Therefore, we get:

b)

μ=183, σ=50, n=50

We need to compute prob of probability that the mean price for a sample of 50 H&R Block retail customers is within $8 of the population mean which means between183 - 8 and 183 + 8 .ie.175 and 191.

Pr(175≤Xˉ≤191). The corresponding z-values needed to be computed are:

Therefore, the following is obtained:

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