1. In order to investigate the feasibility of starting a Sunday edition for a large metropolitan newspaper, information was obtained from a sample of 34 newspapers concerning
their daily and Sunday circulations (in thousands) (source: Gale Directory of Publications, 1994 ). Here is the data set:
Chicago Sun Times
Des Moines Register
Kansas City Star
Los Angeles Daily News
Los Angeles Times
Minneapolis Star Tribune
New Orleans Times-Picayune
New York Daily News
New York Times
Omaha World Herald
Orange County Register
Rochester Democrat & Chronicle
Rocky Mountain News
San Francisco Chronicle
St. Louis Post-Dispatch
St. Paul Pioneer Press
c 2007, Jeffrey S. Simonoff
This data set is available as the files newscirc.*** at the class web site. Please note
that for this homework (only), I am only asking you to answer these questions; no
further analysis, transformation, etc., is necessary.
(a) Draw a scatter plot of Sunday circulation (vertical axis) versus Daily circulation
(horizontal axis). Does the plot indicate that there is a linear relationship between
Daily and Sunday circulation? Why might you have thought that there could be
such a relationship before looking at the data?
(b) Fit a regression predicting Sunday circulation from Daily circulation.
(c) Obtain 95% confidence intervals for β0 and β1 .
(d) Is Daily circulation significantly related to Sunday circulation? Carefully state
the hypotheses you are testing here, and the test you are using.
(e) What proportion of the variability in Sunday circulation is accounted for by Daily
(f) Provide an interval estimate (based on a 95% level) for the true average Sunday
circulation of newspapers with a Daily circulation of 600,000.
(g) The particular newspaper that is being considered as a candidate for a Sunday
edition has a Daily circulation of 600,000. Provide an interval estimate for the
predicted Sunday circulation of this newspaper. How does this interval compare
to the interval in part (f)? From an intuitive point of view, why is this what you
(h) Another newspaper being considered as a candidate for a Sunday edition has
a Daily circulation of 2,500,000. Provide an interval estimate for the predicted
Sunday circulation of this newspaper. How does this interval compare to the
interval in part (g)? Why is this what you would expect?
Note: This homework is not being collected, but all further homeworks should follow a
few basic rules of style. Submit homework on 8.5" by 11" paper only. All sheets, including
computer output, should be this size. Raw computer output is never acceptable; it is up to
you to point out which aspects of the computer output that you submit are relevant and
to demonstrate that they constitute a solution to the problem. Do not scrawl answers on
computer output; your answers should constitute a stand–alone report, with output being
referred to as necessary (“cut and paste” of the output, either literally or electronically, is
encouraged). Please feel free to edit the output so that unnecessary printout is removed.
You should word process your report.
c 2007, Jeffrey S. Simonoff