STAT 3000
Homework assignment 11
Due Wednesday, April 18, 2001
NAME: __________________________
Work on the homework individually or in groups (encouraged - but remember: every
person has to turn in his/her individual assignment sheet). Attach as many sheets of paper
as you need. Show as much work as possible and always write down all formulae you are
using.
You are encouraged to use whatever software you want to solve the problems. Please
indicate which one you have used. For some problems you may attach the original
printout. Two of the problems in this assignment require the data from the diskette
provided in your book. If you don't have that diskette (or if it is defective) and you don't
want to work 'by hand' (all data sets are printed in the book), please come to my office
and bring an empty floppy to obtain a copy of the data.
The number of points for each problem is given in parentheses. You can get a maximum
of 30 points for this homework.
I Sampling Distributions (8 pts)
Please work on the following problems from Chapter 7, Section 7.3:
7.3.3 (2 pts), 7.3.4b(1 pt), 7.3.6 (2 pts)
7.3.12 (2 pts), 7.3.16 (1 pt) à software recommended!
II Understanding Confidence Intervals (4 pts)
1. (2 pts) Here is the Confidence Intervals applet at
http://www.ruf.rice.edu/~lane/stat_sim/conf_interval/index.html
designed to help you understand confidence intervals. Experiment with the applet
and explain in 2 or 3 sentences what it does. Then, explain to someone without
any knowledge in statistics what a confidence interval is, using your own words.
2. (2 pts) Based on your ‘experience’ with the applet, answer briefly the following
questions. (Note: You have to try the applet first. Without looking at the applet,
some of the questions below do not make sense).
1. What percent of the 95% confidence intervals would you expect to contain 50?
2. Which is wider, 95% or 99% confidence intervals? Why?
3. How does sample size affect the number of intervals that contain 50? Explain.
4. How does sample size affect the width of the intervals?
