Amultiple regression model describes the relationship among a collection of cities between y = murder rate

(number of murders per 100,000 residents) and x1 =number of police officers (per 100,000 residents), x2 = median length of prison sentence given to convicted murderers

(in years), x3 = median income of residents of city

(in thousands of dollars), and 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 explanatory variables, software reports the estimated standardized regression coefficients of

−0.075 for x1, −0.125 for x2, −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 x1, x2, and x3, and one standard deviation below the mean on x4.

Interpret.