Question

The maintenance department at the main campus of a large state university receives daily requests to replace fluorecent lightbulbs. The distribution of the number of daily requests is bell-shaped and has a mean of 39 and a standard deviation of 8. Using the 68-95-99.7 rule, what is the approximate percentage of lightbulb replacement requests numbering between 31 and 39? Do not enter the percent symbol. ans = Incorrect % Get help: VideoVideo Box 1: Enter your answer as an integer or decimal number. Examples: 3, -4, 5.5172 Enter DNE for Does Not Exist, oo for Infinity LicensePoints possible: 1

Answer 1

As per 68-95-99.7 rule , 68 % of values lie within the one standard deviation from mean and vice versa.

Here, mean = 39 , std deviation = 8

So, 68 % of values lies in the range of 31 to 47

Now since a bell curve is symmetrical about the mean. So, the area on right and left side of mean must be equal for equal deviations from mean.

In other words, 34% of values will lie in the range 31 to 39 and the remaining 34% in the range 39 to 47.

So,  the approximate percentage of light bulbs replacement request in the range of between 31 to 39 is 34 percent.

so, final answer is 34