Question

The time it takes to process phone orders in a small florist/gift shop is normally distributed with a mean of 6 minutes and a standard deviation of 3 minutes. What cutoff value would separate the 2.5% of orders that take the most time to process?
A) 4.76 minutes
B) 3.52 minutes
C) 10.01 minutes
D) 11.00 minutes
E) 12.00 minutes

Answer 1

E) 12 minutes

A normal curve has approximately 95% of graph between mean - 2sd and mean + 2sd
So 95% of the times will be between 0 and 12 minutes. 6 - 2x3 to 6 + 2x3
2.5% will take over 12 minutes

Strangely 2.5% will also take less than 0 minutes to process which shows the normal curve is not perfect in this example.