Question

The physical plant at the main campus of a large state university recieves daily requests to replace fluorescent lightbulbs. The distribution of the number of daily requests is bell-shaped and has a mean of 52 and a standard deviation of 5. Using the empirical rule, what is the approximate percentage of lightbulb replacement requests numbering between 47 and 52

Answer 1

34% of lightbulb replacement requests numbering between 47 and 52

Explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 52

Standard deviation = 5

Between 47 and 52:

52 is the mean and 47 is one standard deviation below the mean.

By the Empirical Rule, 68% of the measures are within 1 standard deviation of the mean.

Since the normal distribution is symmetric, of those, 34% are within 1 standard deviation below the mean and the mean(47 and 52) and 34% are within the mean and one standard deviation above the mean(52 and 57).

So

34% of lightbulb replacement requests numbering between 47 and 52