Suppose that the Buffalo BrewPub wants to improve it's beer.  The brewery is
interested in the way that different varieties of hops and different bottling
techniques influence the bitterness of the beer and, ultimately, it's
drinkability.  In order to examine these issues, the brewery brews 40 bottles
of beer, differing in only the following manner.  First, half of the bottles
are green and half are brown.  Furthermore, in the green bottles, half are
flavored with Cascade hops and half with Bullion hops.  A similar 50-50
flavoring was done with the brown bottles.  After bottling, the bitterness of
each bottle is measured in IBUs, which stands for International Bittering
Units--the higher the IBU, the more bitter the beer.  Also, a small portion of
each bottle is consumed and rated for overall drinkability using QBUs (Quality
Brew Units).  Finally, the bottles are exposed to ultraviolet light, to simu-
late storage on a grocery store shelf.  Ultraviolet light is known
to cause a distasteful "skunky" flavor, which the brewer hopes the bottles
will prevent.  After exposure, the beers are tasted again, and it is noted
whether or not they are skunky.
 
The data file you will receive contains data relevant to the above situation.
You may assume that IBUs and QBUs are interval-level variables.
 
The format of the file is as follows:
 
Column      Variable                Comment
 1-2        Bottle ID
  3         Hop Variety             1 = Cascades; 2 = Bullions
  4         Bottle                  1 = green; 2 = brown
  5         Skunkiness              1 = yes; 2 = no
 7-8        Bitterness              measured in IBUs
10-14       Drinkability            measured in Quality Units
 
Answer the following questions:
 
1.  What effect does hop variety and bottle color have on bitterness?  (Be
sure to check residuals and homogeneity of variance.)
 
2.  Generate a scatterplot showing how bitterness affects drinkability.  Use a
regression routine to analyze the quantitative effects of bitterness on
drinkability.  Be sure to check the residuals.  (Hint #1:  Examine a
scatterplot.  Hint #2:  Recall that a parabola is a second degree polynomial.
Hint #3:  Come up with a transformation that linearizes the hypothesized
model.)
 
3.  How do hop variety and bottle color contribute to the skunkiness caused by
ultraviolet light?
 
Give complete answers to the above questions, pointing to relevant parts of
your output.