Question

How would you use a completely randomized experiment in each of the following settings? Is a placebo being used or not? Be specific 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.
A- Use random selection to pick 5 calves to inoculate.
B- No placebo is being used.
C- After inoculation, test 5 calves to see if there is a difference in resistance to infection between the two groups.
D- After inoculation, test 10 calves to see if there is a difference in resistance to infection between the two groups.Use random selection to pick 10 calves to inoculate.
E- A placebo is used for the remaining 12 calves.
F- After inoculation, test all calves to see if there is a difference in resistance to infection between the two groups.
(b) The Denver Police Department wants to improve its image with teenagers. A uniformed officer is sent to a school one day a week for 10 weeks. Each day the officer 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. (Select all that apply.)
A- After the police visits, survey all the schools to see if there is a difference in views between the two groups.
B- After the police visits, survey 9 of the schools to see if there is a difference in views between the two groups.
C- No placebo is being used.
D- A placebo is used for the remaining 9 schools.
E- Use random selection to pick nine schools to visit.
F- Use random selection to pick 18 schools to visit.
(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 the two months, each subject is surveyed regarding his or her current smoking habits.
A- Then record the smoking habits of the 35 volunteers to see if a difference exists between the two groups.
B- No placebo is being used.
C- Use random selection to pick 35 volunteers for the skin patch with the drug.
D- Then record the smoking habits of the 40 volunteers to see if a difference exists between the two groups.
E- Use random selection to pick 40 volunteers for the skin patch with the drug.
F- A placebo patch is used for the remaining 35 volunteers in the second group.
G- Then record the smoking habits of all volunteers to see if a difference exists between the two groups.

Answer 1

Answer:

(a)

Use random selection to pick 10 calves to inoculate.(you didn't mention this option in the question instead you mix it with other option)

(B).No placebo is being used.

(F).After inoculation, test all calves to see if there is a difference in resistance to infection between the two groups.

(b)

(C).No placebo is being used.

(E).Use random selection to pick nine schools to visit.

(A).After the police visits, survey all the schools to see if there is a difference in views between the two groups.

(c)

(F.)A placebo patch is used for the remaining 35 volunteers in the second group.

(E).Use random selection to pick 40 volunteers for the skin patch with the drug.

(G).Then record the smoking habits of all volunteers to see if a difference exists between the two groups.

Step-by-step explanation:

In question one the answer is mixed with other option so the correct answer statements are provided along with the option for all questions. Placebo is not used in question (a) scenario because it is mentioned in the statement that there is enough vaccine is present and sample of 10 calves is selected from 22 calves and we test all calves after the inoculation because it is mention that blood test should be done on all calves.

Placebo is not used in question (b) scenario because it is mentioned in the statement that the police department can visit half of 18 schools and random sample of 9 schools are selected and it is mentioned in the statement that survey is sent to all 18 school so after the police visit all schools are surveyed to see the difference in views

Placebo patch is used in question (c) because it is mentioned in the statement that 40 out of 75 received the new skin patch so, the remaining 35 received placebo patch and random sample of 40 volunteers are selected for new skin patch. It is mentioned in the statement that each subject is survey so in the end smoking habits of all volunteers are recorded.