A police department in a large city wants to boost its image among youths. They want to know if having a police officer present at school activities would affect their image with teenagers. Nine of the city's 18 high schools were chosen at random to have a police officer visit one day a week for ten weeks. Every time, the officer engages constructively with pupils. The district's remaining 9 high schools have no police officers assigned to them. After ten weeks, all 18 schools get a poll about how youth see the police.

The survey findings are compared to see if there is a difference in attitudes between schools where an officer is present and those where an officer is not present.

A) In this study, the treatment is:

1) view of police officers according to the survey. 2) presence, or lack of presence, of a police officer at the school. 3) number of weeks the officer was present at the school. 4) number of schools in the city.

B) The control group in this study is the:

1) group of schools with an officer present one day a week. 2) number of weeks the officer was present at the school. 3) group of schools with no officer present. 4) the presence of a police officer at the school.

C) The experimental units in the study are the:

1) students at the schools. 2) 18 schools in the city. 3) students who interacted with police officer. 4) officers at the schools.

D) This experiment is an example of a(n):

1) confounded, nonrandomized study. 2) observational study. 3) completely randomized design. 4) randomized complete block design.