Question

In: Statistics and Probability

A company services copiers. A review of its records shows that the time taken for a...

A company services copiers. A review of its records shows that the time taken for a service call is a normally distributed random variable with a mean of 150 minutes and a standard deviation of 40 minutes.

a. What proportion of service calls takes less than 2 hours?

b. What proportion of service calls takes between 120 and 180 minutes?

c. Find the 99% quantile of the distribution and interpret the result.

d. Suppose that the times of the subsequent service calls are independent. Find the 99% quantile of the distribution of the overall time taken for two consecutive service calls and interpret the result.

Solutions

Expert Solution

a)

2 hours = 2*60 = 120 minutes

b)

c)

Answer: 243.20 minutes

d)

Let T shows the total time taken by two consecutive calls call X1 and X2. Given that

Since X1 and X2 are normally distributed so T will also normally distributed with following parameters

So required 99 quantile will be

Answer: 431.80 minutes


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