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A made-up trial of a cream for a rash puts 160 patients in a cream group and 160 in a placebo…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A made-up trial of a cream for a rash puts 160 patients in a cream group and 160 in a placebo group, by random assignment. In the cream group, 104 patients improve. In the placebo group, 72 improve. Find the percentage who improve in each group, and the effect of the cream in percentage points.
Need a reminder? The key ideaShow
A fair experiment has a control group, random assignment, a placebo where it helps, blinding and enough subjects. The effect of the treatment is the difference between the two groups, in percentage points or in the units of the response.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The cream group. .
Step 2. The placebo group. .
Step 3. The effect. percentage points.
Answer: , and an effect of percentage points.
Watch out. The makers might say "65% improve". Without the placebo group, nobody would see that 45% improve anyway.
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