Homework 1 1. In order to investigate the feasibility of starting a

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Homework 1
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:
Newspaper
--------Baltimore Sun
Boston Globe
Boston Herald
Charlotte Observer
Chicago Sun Times
Chicago Tribune
Cincinnati Enquirer
Denver Post
Des Moines Register
Hartford Courant
Houston Chronicle
Kansas City Star
Los Angeles Daily News
Los Angeles Times
Miami Herald
Minneapolis Star Tribune
New Orleans Times-Picayune
New York Daily News
New York Times
Newsday
Omaha World Herald
Orange County Register
Philadelphia Inquirer
Pittsburgh Press
Portland Oregonian
Providence Journal-Bulletin
Rochester Democrat & Chronicle
Rocky Mountain News
Sacramento Bee
San Francisco Chronicle
St. Louis Post-Dispatch
St. Paul Pioneer Press
Tampa Tribune
Washington Post
c 2007, Jeffrey S. Simonoff
Daily
----391.952
516.981
355.628
238.555
537.780
733.775
198.832
252.624
206.204
231.177
449.755
288.571
185.736
1164.388
444.581
412.871
272.280
781.796
1209.225
825.512
223.748
354.843
515.523
220.465
337.672
197.120
133.239
374.009
273.844
570.364
391.286
201.860
321.626
838.902
Sunday
-----488.506
798.298
235.084
299.451
559.093
1133.249
348.744
417.779
344.522
323.084
620.752
423.305
202.614
1531.527
553.479
685.975
324.241
983.240
1762.015
960.308
284.611
407.760
982.663
557.000
440.923
268.060
262.048
432.502
338.355
704.322
585.681
267.781
408.343
1165.567
1
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
circulation?
(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
would expect?
(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
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