Mario has a pizzeria. The times to prepare and deliver pizzas are normally distributed with mean 20 minutes and standard deviation 5 minutes. Use the empirical rule to find an interval in which about 95% of the times will lie.
A) (15 minutes, 25 minutes)
B) (10 minutes, 30 minutes)
C) (5 minutes, 35 minutes)
D) (0 minutes, 40 minutes)

Question

Mario has a pizzeria.  The times to prepare and deliver pizzas are normally distributed with mean 20 minutes and standard deviation 5 minutes.  Use the empirical rule to find an interval in which about 95% of the times will lie.
 A) (15 minutes, 25 minutes) 
B) (10 minutes, 30 minutes) 
C) (5 minutes, 35 minutes) 
D) (0 minutes, 40 minutes)

amistre64 · Answer

whats the sd for 95%?  1 2 or 3 sds?

amistre64 · Answer

if you can recall the empirical rules, then the question basically answers itself :)

kropot72 · Answer

The empirical rule says that about 95% of the area under the nornal distribution curve is included within a distance of about +- 2 standard deviations from the mean.
In this case 2 standard deviations = 2 * 5 = 10 minutes.
The lower limit of the interval = 20 - 10 minutes
The upper limit of the interval = 20 + 10 minutes.

Can you now finish it?