Question

Ten subjects are being studied to test the effectiveness of itch relief for three types of medication: A, B, and C. Using a 10-point scale, the researcher calculates the subjects' amount of itching
before treatment compared with the amount of itching after treatment. The response variable is the itch rating after one hour of treatment. Previous studies have shown the effects of
treatment may vary based on a subject's pain resistance. How should the subjects be blocked? Explain. (4 points)
They should be blocked alphabetically so the subjects are as different as possible.
They should be blocked by age because older subjects tend to itch more.
They should be blocked by gender because female subjects tend to itch more.
They should be blocked by pain resistance so the subjects are as similar as possible.
O Blocking should not be used in this experiment.

Answer 1

Answer: Choice C

They should be blocked by pain resistance so the subjects are as similar as possible.

============================================================

Explanation:

The process of blocking in statistics is where we group up people in blocks, and each block is determined by a characteristic of some sort. In this case, we're grouping people up by pain resistance level. Those very resistant to pain will be in one group, while those who easily feel pain will be in another block, and so on. It might be effective to have a pain scale and sort people by that.

Blocking is done so that we eliminate unwanted variability. We are testing the effectiveness of the itching cream, so all we care about is if the itch reduces or not. We aren't worried about the levels of pain. However, it says that "Previous studies have shown the effects of treatment may vary based on a subject's pain resistance". So we group up the people by pain tolerance to help eliminate the variability of pain tolerance levels.

This is why choice C is the final answer.

-------------

Extra info:

• Choice A is false because a person's name doesn't have anything to do with if the treatment works or not.
• Choice B is false because we weren't given any info to indicate it being true. It may be true, but we simply don't have enough info to confirm it.
• Choice C is false for similar reasons as choice B.

Answer 2

Answer:D

Step-by-step explanation:

This is due to the question explicitly stating how the previous studies have shown the effects of treatment may vary based on a subjects pain resistance. This leads to the only option that relates to the study's background, D