To determine the publics opinion of the police department, the police chief obtains a cluster sample of

Question:

To determine the public’s opinion of the police department, the police chief obtains a cluster sample of 15 census tracts within his jurisdiction and samples all households in the randomly selected tracts. Uniformed police ofﬁcers go door to door to conduct the survey.
The survey has bias.
(a) Determine the type of bias.
(b) Suggest a remedy.