Business Applications of Multiple Regression

CORRELATION ANALYSIS 17

Public Transportation Ridership

Table 1.5

3

shows the largest urbanized areas by population, unlinked

passenger trips,

4

and passenger miles for 2008. Figure 1.6 shows the rela-

tionship between unlinked passenger trips and population. Notice that

almost all the data points are clustered in the bottom left corner of the

chart. That is because the New York system has so many more trips (over

4 million versus the next highest of about 700,000) and such a higher

population (almost 18 million versus the next highest of almost 12 mil-

lion) that its observation overpowers the remaining observations. This

type of observation outside the usual values is called an outlier.

5

Figure

1.7 shows the same chart with ...