Page 45 - Statistics II for Dummies

Chapter 2: Finding the Right Analysis for the Job 29

Suppose you’re an avid golfer and you want to figure out how much time you
should spend on your putting game. The question is this: Is the number of
putts related to your total score? If the answer is yes, then spending time on
your putting game makes sense. If not, then you can slack off on it a bit. Both
of these variables are quantitative variables, and you’re looking for a connec-
tion between them. You collect data on 100 rounds of golf played by golfers
at your favorite course over a weekend. Following are the first few lines of
your data set.

Round Number of Putts Total Score
1 23 76
2 27 80
3 28 80
4 29 80
5 30 80
6 29 82
7 30 83
8 31 83
9 33 83
10 26 84

The first step in looking for a connection between putts and total scores (or
any other quantitative variables) is to make a scatterplot of the data. A scat-
terplot graphs your data set in two-dimensional space by using an X,Y plane.
You can take a look at the scatterplot of the golf data in Figure 2-1. Here, x
represents the number of putts, and y represents the total score. For exam-
ple, the point in the lower-left corner of the graph represents someone who
had only 23 putts and a total score of 75. (For instructions on making a scat-
terplot by using Minitab, see Chapter 4.)

Scatterplot of Total Score versus Number of Putts
120

110
Figure 2-1:
The two- Total Score 100
dimensional
scatterplot 90
helps you
look for
relation- 80
ships in
data. 20 25 30 35 40 45 50
Putts

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