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? A)44.75 B)46.75 C)47.50 D)52.50 Using Excel =NORM.INV(.75,40,10) = 46.75, or Q₃ = 40 + 0.675(10) = 46.75 using AppendixC.

Question

Quizplus · Accepted Answer

To find the third quartile, we need to find the value that separates the top 25% of the distribution. Using the formula z = (x - μ) / σ and looking up the z-score for the 75th percentile (0.675) in a standard normal distribution table or using Excel's NORM.INV function, we find that the corresponding value of x is 46.75 minutes. Therefore, the third quartile for the time required to complete the form is 46.75 minutes.

The Time Required for a Citizen to Complete the 2010