The second part of the TV sales problem requires calculation
of the 90th percentile of the demand histogram.
In mathematical notation, we are looking for *a* such that
*P*(*X*>*a*)=.10. See Figure 4.4.

Example:To find the 90th percentile of TV sales, type the inputs (.90, 36, 8). The answer is 46.25, or approximately 46.

Exercise:Find the following percentiles for TV sales. Guess the percentile first, then use your calculator. Was your guess close?

a. 80th percentile

b. 20th percentile

c. 50th percentile