Speedy Lube: Length of Time to Complete a Service Oil Change

The length of time to do a complete full service oil change at Speedy-Lube is normally distributed with a meanof 15.8 minutes and a standard deviationof 2.2 minutes.

X P(X < x) P(X > x) Mean Std dev
11 .0146 .9854 15.8 2.2
15 .3581 .6419 15.8 2.2
21 .9910 .0090 15.8 2.2
24 .9999 .0001 15.8 2.2
p(lower) p(upper)

(A) Analyze the output above to determine what percentage of complete full service oil changes will fall between 21 and 24 minutes.

(B) What percentage of complete full service oil changes will take more than 21? If 1000 cars had a complete full service oil change, how many would you expect to be finished in more than 21 minutes?

This solution determines the length of time it takes to complete a full service oil change for Speedy Lube.