General: Completely Randomized Experiment How would you use a completely randomized experiment in each of the following settings? Is a placebo being used or not? Be specifi c and give details.

(a) A veterinarian wants to test a strain of antibiotic on calves to determine their resistance to common infection. In a pasture are 22 newborn calves.

There is enough vaccine for 10 calves. However, blood tests to determine resistance to infection can be done on all calves.

(b) The Denver Police Department wants to improve its image with teenagers.

A uniformed offi cer is sent to a school one day a week for 10 weeks.

Each day the offi cer visits with students, eats lunch with students, attends pep rallies, and so on. There are 18 schools, but the police department can visit only half of these schools this semester. A survey regarding how teenagers view police is sent to all 18 schools at the end of the semester.

(c) A skin patch contains a new drug to help people quit smoking. A group of 75 cigarette smokers have volunteered as subjects to test the new skin patch. For one month, 40 of the volunteers receive skin patches with the new drug. The other volunteers receive skin patches with no drugs. At the end of two months, each subject is surveyed regarding his or her current smoking habits.