How would you use a completely randomized experiment in each of the following se
ID: 3297518 • Letter: H
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. (Select all that apply.) Use random selection to pick 5 calves to inoculate. After inoculation, test 10 calves to see if there is a difference in resistance to infection between the two groups. A placebo is used for the remaining 12 calves. No placebo is being used. After inoculation, test all 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. After inoculation, test 5 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.) No placebo is being used. Use random selection to pick 18 schools to visit. A placebo Is used for the remaining 9 schools. After the police visits, survey all the schools to see if there is a difference in views between the two groups. After the police visits, survey 9 of the schools to see if there is a difference in views between the two groups. Use random selection to pick nine 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 regarding his or her is current smoking habits. (Select all that apply.) A placebo patch is used for the remaining 35 volunteers in the second group. Use random selection to pick 35 volunteers for the skin patch with the drug. Then record the smoking habits of the 35 volunteers to see if a difference exists between the two groups. Use random selection to pick 40 volunteers for the skin patch with the drug. Then record the smoking habits of the 40 volunteers to see if a difference exists between the two groups. Then record the smoking habits of all volunteers to see if a difference exists between the two groups. No placebo is being used.Explanation / Answer
In a completely randomized design, all experimental units have an equal chnace of being receiving any treatment. A treatment known to have no effect is administered to one group so that all group experience the same conditions. Many groups respond to such a treatment (a response knwon as placebo effect). Only by comparing with a placebo effect one can be sure that the observed effect of a treatment is not due simply to the placebo effect.
a) There are 22 newborn calves and vaccine for 10 are avilable. Therefore, use random selection to pick 10 calves to innoculate. A placebo is used for the remianing 12 calves. After innoculation test all calves to see if there is a difference in resistance to infection between the two groups.
b) There are 18 schools and police department can visit 9 schools.Use random selection to pick nine schools to visit. A placebo is used for remaining 9 schools. After the police visits, survey all schools to see if there is a difference in views between two groups.
c) There are 75 smokers and 40 of them receive skin patches with new drug and remaining 35 smokers didnot receive skin patches with no drugs. Use random selection to pick 40 volunteers for the skin patch with drug. A placebo patch is used for the remaining 35 volunteers in the second group. Then record the smoking habits of all volunteers to see if a difference exists between two groups.
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