What variation there is does not appear to follow any meaningful pattern, with one exception. There is a tendency for residents living in the 28401 zip code to rate the police department slightly lower than residents in other zip codes. The telephone survey was conducted over the six day period of February 6-11, 1999. UNCW students participating in a class project completed 482 interviews of Wilmington residents. Telephone numbers were randomly generated by computer.
Randomization maximizes the representativeness of the sample by including unlisted numbers.
Because the survey was of Wilmington residents only, respondents were screened by the interviewer to determine if they were a current city resident. Thus, residents of newly annexed sections of the city only a week prior to this survey were included. Interviews were spread out over four evenings, one Saturday morning, and a Thursday afternoon to increase the probability of reaching residents at home. Interviews took approximately eight minutes. The rate of refusal to answer the survey was 39 percent which is typical for this type of survey.