The U.S. Department of Justice collects data on involuntary citizen contacts with police, specifically those that occur when the person is the driver of a motor vehicle (that is, traffic stops) or when the person is stopped by the police while in a public place but not in a moving vehicle (that is, street stops). One item of interest is public perception of police behavior and police legitimacy during traffic and street stops. (Source: Matthew Durose and Lynn Langton, "Police Behavior During Traffic and Street Stops, 2011," Bureau of Justice Statistics,NCJ 242937, September 24, 2013, http://www.bjs.gov/index.cfm?ty=pbdetail&iid=4779.)Suppose you are involved in a related study that examines public perception of police behavior during traffic stops in your city. You survey 3,497 drivers who were stopped by police while operating a motor vehicle. You collect information about the enforcement action that was taken by the police (that is, whether the driver was ticketed) and on the driver's perception of police behavior during the stop. The results are shown in the following bivariate table. Note that the table includes the value of chi square for this data.

	Enforcement Action (X)
Driver's Opinion (Y)	Ticketed	Not Ticketed	TOTALS
Police behaved properly	1,463	1,559	3,022
Police did not behave properly	321	154	475
TOTALS	1,784	1,713	3,497
			Chi square = 60.16, df = 1, p < 0.001.

You are interested in the possible association between the type of enforcement and driver perception of police behavior. Since you have a 2 x 2 bivariate table with nominal-level variables, you decide to use phi to measure the association between these variables. Calculate phi for these data:

Phi =

The result indicates a relationship between the type of enforcement and the perception of police behavior.