 
Summary: Exam 3 for Introductory Statistics
Prof. Bernardo Ábrego Math 140, Spring 2006
Name. 05/04/06
Directions.
· You have 1 hour and 50 minutes to complete the test.
· You can use a 3"×5" card with notes, your calculator, and the ztables provided on the back of this
test. No other materials are allowed.
· No scratch paper is permitted. For this purpose or in case you need more space you can use the back
of the pages of the test.
1. A recent study of 100 people in Miami found 27 were obese. Find the 99% confidence interval of the
population proportion of individuals living in Miami who are obese.
n = 100 is the sample size, ^p = 27/100 = 0.27 is the sample proportion. For 99% confidence we use
z
= 2.576. So the interval is given by ^p ± z
q
^p(1^p)
n which gives,
(0.15564, 0.38436)
2. A university dean of students wishes to estimate with 95% confidence the average number of hours
students spend doing homework per week. It has been estimated that the population standard deviation
