Additional Homework Problems - Pearson

4.61 The accountant at Rick Wing Coal Distributors, Inc., in San Francisco notes that the demand for coal
seems to be tied to an index of weather severity developed by the U.S. Weather Bureau. When weather was
extremely cold in the U.S. over the past 5 years (and the index was thus high), coal sales were high. The
accountant proposes that one good forecast of next year’s coal demand could be made by developing a
regression equation and then consulting the Farmer’s Almanac to see how severe next year’s winter would
be. For the data in the following table, derive a least squares regression and compute the coefficient of
correlation of the data. Also compute the standard error of the estimate.
Coal Sales (in millions of tons), y 4 1 4 6 5
Weather Index, x 2 1 4 5 3
4.62 Given the following data, use least squares regression to develop a relation between the number of
rainy summer days and the number of games lost by the Boca Raton Cardinal baseball team.
Years 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Rainy Days 15 25 10 10 30 20 20 15 10 25
Games Lost 25 20 10 15 20 15 20 10 5 20
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