11.29. A multiple regression model describes the relationship among a collection of cities between y = murder rate (number of murders per 100,000 residents) and x\ = Number of police officers (per 100,000 residents)

X2 = Median length of prison sentence given to convicted murderers (in years)

xt, = Median income of residents of city (in thousands of dollars)

X4 = Unemployment rate in city These variables are observed for a random sample of 30 cities with population size exceeding 35,000. For the model with these predictors, software reports the estimated standardized regression coefficients of —0.075 for xj, —0.125 forx2, —0.30 for X3, and 0.20 for X4.

(a) Write the prediction equation using standardized variables.

(b) Which explanatory variable has the greatest partial effect on y? Explain.

(c) Find the predicted z-score on murder rate for a city that is one standard deviation above the mean on jq, jq, and X3, and one standard deviation below the mean on X4. Interpret.