Statistics 68-95-99.7 Rule

Question

The physical plant at the main campus of a large state university recieves daily requests to replace florecent lightbulbs. The distribution of the number of daily requests is bell-shaped and has a mean of 54 and a standard deviation of 8. Using the 68-95-99.7 rule, what is the approximate percentage of lightbulb replacement requests numbering between 54 and 62?

Answer 1

Since your standard deviation is 8 and your mean is 54, from 54 to 62 is the section of the bell curve between the mean and 1 standard deviation *above*. 68% of cases will be *within* 1 standard deviation of the mean, but that's plus OR minus a standard deviation. Since you are only looking UP by 1 standard deviation and not in both directions, divide 68 by 2. This means that 34% of days should have between 54 and 62 cases.