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.)
No placebo is being used. A placebo is used for the remaining 12 calves. After inoculation, test 5 calves to see if there is a difference in resistance to infection between the two groups. After inoculation, test 10 calves to see if there is a difference in resistance to infection between the two groups. 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 5 calves to inoculate. Use random selection to pick 10 calves to inoculate.

Answer 1

Correct options are,

No placebo is being used

After inoculation, test 10 calves to see if there is a difference in resistance to infection between the two groups.

Explanation: Since the test are being performed on calves, there is no psychological effect of vaccination is involved so there is no need to use placebo.

Since there is enough vaccine for 10 calves so randomly select 10 calves out of 22 and after inoculation test the difference in resistance to infection between the two groups.