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The maintenance department at the main campus of a large state university receives daily requests
to replace fluorescent lightbulbs. The distribution of the number of daily requests is bell-shaped
and has a mean of 60 and a standard deviation of 7. Using the 68-95-99.7 rule,
what is the approximate percentage of lightbulb replacement requests numbering between 60 and 81?
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Notice that in this problem 81 is three standard deviations from the mean of 60.
The Empirical Rule states that 99.7% of data observed following a normal distribution
lies within 3 standard deviations of the mean.
Since the normal distribution is symmetric, we may conclude that the pecentage of lightbulb
replacement requests numbering between 60 and 81 is half of 99.7%, i.e. 49.85%. ANSWER
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