Question

The time required for a citizen to complete the 2010 u.s. census "long" form is normally distributed with a mean of 40 minutes and a standard deviation of 10 minutes. what is the third quartile (in minutes) for the time required to complete the form? 44.75 46.75 47.50 52.50

Answer 1

The third quartile will be evaluated as follows:
z-score=(x-mu)/sig
mu=40
sig=10
the z-value corresponding to 0.75 is 0.68
hence:
0.67=(x-40)/10
solving for x we get:
6.7=x-40
x=6.7+40
x=46.7
x~46.75