Compute the correlation between amount of violent crime and each of the other variables (graduation rate, police officer wage, correctional officer wage). Which of the three would be the best predictor of amount of violent crime.

The best predictor of violent crime is the police officer wage.

Explanation:

The police officer wage and correctional officer wage is related to the govenrment budget for security, which is calculated according to the society's needs. In consequence, this two factors are strictly related with the amount of violent crime in the city, in particular, the police officer wage because this person works directly with the society.

The graduation rate, on the other hand may vary for other several reasons rather crime such as lack of capital, personal reasons, family, etc.