2.1. Consider the following regression model, which purports to predict the length of sentence given to individuals convicted of theft: y ¼ b0 þ b1x þ e where y ¼ length of sentence, and x ¼ number of prior sentences.

(a) List the variables you might wish to include in a more comprehensive model. Include a brief statement about why each additional variable should be included. (b) Present your model in equation form