2.53 The influence of Texas

CASE 2.1 Make a plot similar to Figure 2.16 giving regression lines with and without Texas. Summarizewhat this plot describes.

California, Texas, Florida, and New York are somewhat unusual and might be considered outliers. However, these cases are not influential with respect to the least-squares regression line.

Influential cases may have small residuals because they pull the regression line toward themselves. That is, you can’t always rely on residuals to point out influential observations. Influential observations can change the interpretation of data. For a linear regression, we compute a slope, an intercept, and a correlation. An individual observation can be influential for one of more of these quantities.