18. Refer to Table 91, not including the observation for DC. Let Z be a dummy variable for whether a state is in the South. with Z=1 for AL. AR. FL. GA KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV

a) Analyze the relationship between Y = violent crime rate and the predictors X = poverty rate and Z.

b) Add percentage white as a predictor. Find a model that describes the data well, and interpret,

c) Repeat the analysis with D.C in the data set, setting Z=1 for it. Do the conclusions change in any way?