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Question

In a mid-size company, the distribution of the number of phone calls answered each day by each of the 12 receptionists is bell-shaped and has a mean of 57 and a standard deviation of 8. Using the empirical rule (as presented in the book), what is the approximate percentage of daily phone calls numbering between 41 and 73?

Answer 1

You are being asked to determine the percentage of daily phone calls that range between the mean and plus/minus 2 standard deviations (57 - 2•8 = 41 and 57 + 2•8 = 73).

The normal curve looks like this:

You'll notice that the percentages that lie between -2 standard deviations and + 2 standard deviations is 13.6 + 34.1 + 34.1 + 13.6 = 95.4%

So there are approximately 95% of the days where the number of phone calls is between 41 and 73.