Chapter 3 Working with Charts 87Figure 3-3The Big Ten
workbook
2 Save the fi le as Big Ten Graduation Chart.
A school with a low graduation rate among its student-athletes is vulner-
able to investigation and possible sanctions on the part of the NCAA. We’re
going to explore the relationship between the average SAT score from classes
of incoming fi rst-year students and the percentage of those students in those
classes who eventually graduate within six years of entering college.
One question we might ask is: Do incoming classes with high average
SAT scores have higher rates of graduation? Is this true for all universities?
We’ll get a visual picture of this relationship by producing a scatter plot.
A scatter plot is a chart in which observations are represented by points
on a rectangular coordinate system. Each observation consists of two values:
One value is plotted against the vertical or y axis, and the second value is
plotted against the horizontal or x axis (see Figure 3-4). In Figure 3-4 we are
plotting a point with x = 3 and y = 5.