Police officers often have to call Child Protection Services (CPS) when responding to a call for service. However, when they encounter CPS workers, they are not always satisfied. The national average level of satisfaction police officers have with CPS workers is 6.5 (on a scale of 0-10, with 10 being most satisfied). The head of CPS in Phoenix wants to see if the satisfaction levels of the police with CPS are different in Phoenix. He talks to 200 Phoenix police officers and finds the average satisfaction level is 7.8, with a standard deviation of 2.7. Conduct a hypothesis test to determine if the Phoenix police officers' average level of satisfaction is truly different than the national average. Use a significance level of 0.01.

In the above hypothesis test, what is the test statistic?