Question

2. In a study investigating placebo pain pills, researchers randomly assigned 82 healthy people to two groups. The first group received placebo pills, and was told they were a new fast, acting pain reliever that cost $2.50 each. The second group received the same placebo pills, but was told the pills were $.10 each. Each group received a mild electrical shock before and after taking the pills. They were then asked if the pills reduced the pain. In the first group (with the expensive pills), 85% said the pills were effective. In the second group (with the discount pills), 61% said they were effective.

a. Provide a 99% confidence interval for the difference between the two groups. b. What are the possible research questions for this study? (Hint: Decide on what the possible hypotheses could be, and then figure out what questions these could address.) (show work without using software to solve)

Answer 1

Let us assume that the two groups contains equal number of people .

Let , n₁ : Number of people in the first group receiving treatment that costs $2.50

n₂ : Number of people in the second group receiving treatment that costs $0.10

Define , : Population proportion of persons in the first group who said that the pills were effective

: Population proportion of persons in the second group who said that the pills were effective

a ) The 99 % confidence interval for is :

where ,

Required confidence interval :  

b ) From the data providede here , we can find out whether expensive pills are more effective in reducing pain than discount pills . That is ,