Question

a pharmaceutical company is developing a new oral medication for the treatment of psoriasis, a skin disease marked by red, itchy, scaly patches. describe how you could design a cont to test the effect of the medication. how could you keep participants from knowing whether they were in the treatment group?
choose the correct answer below
a. randomly select a sample of people with psoriasis. assign the most severe cases to one group and the mildest cases to the other group. give the group with the most severe cas the treatment, and withhold it from the other group. give both groups similar looking pills, so neither knows which group they are in.
b. randomly select a sample of people with psoriasis. assign the most severe cases to one group and the mildest cases to the other group. give the group with the most severe cas the treatment, and withhold it from the other group. give the treatment group the pill and the control group nothing, so neither knows which group they are in
c. offer a $100 voucher to collect a sample of volunteers. randomly assign them to one of two groups. give one group the treatment, and withhold it from the other group. give both looking pills, so neither knows which group they are in.
d. randomly select a sample of people with psoriasis. randomly assign them to one of two groups. give one group the treatment, and withhold it from the other group. give the treatm pill and the control group nothing, so neither knows which group they are in.
e. randomly select a sample of people with psoriasis. randomly assign them to one of two groups. give one group the treatment, and withhold it from the other group. give both grou looking pills, so neither knows which group they are in.
f. offer a $100 voucher to collect a sample of volunteers. assign people with psoriasis to one group and people without it to another group. give the group of people with psoriasis the and withhold it from the other group. give the treatment group the pill and the control group nothing, so neither knows which group they are in

Explanation:

• Option A: Assigning based on case severity (most severe vs mildest) is not random assignment. Random assignment is crucial in experimental design to avoid bias. So this option is incorrect.
• Option B: Similar to option A, non - random assignment (based on case severity) is a flaw. Also, giving the control group nothing can lead to psychological differences (e.g., participants in the control group may feel neglected) that can confound results. Placebo (similar - looking pills) is better.
• Option C: Offering a $100 voucher can introduce selection bias. Volunteers who are attracted by the voucher may not be representative of the general population of psoriasis patients.
• Option D: Giving the control group nothing can lead to psychological differences (e.g., participants in the control group may feel neglected) that can confound results. Placebo (similar - looking pills) is better.
• Option E: Randomly select psoriasis patients (representative sample), randomly assign (to avoid bias), give one group treatment and the other a placebo (similar - looking pills to keep participants blind). This follows good experimental design principles.
• Option F: Offering a $100 voucher can introduce selection bias. Also, including non - psoriasis patients in the control group is incorrect as the treatment is for psoriasis.

Answer:

E. Randomly select a sample of people with psoriasis. Randomly assign them to one of two groups. Give one group the treatment, and withhold it from the other group. Give both groups looking pills, so neither knows which group they are in.