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.

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:

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step-by-step explanation:

answer:   28.56 feet (approx)

step-by-step explanation:

since, triangle abc has measure of angle c equal to 55 degrees, measure of angle abc equal to 90 degrees, and length of bc equal to 20 feet.

we have to find out the measurement of segment ab.

therefore, tan 55° =

but bc = 20 feet.

⇒ tan 55 ° =  

⇒ ab = 20 × tan 55 °

⇒ ab = 20 × 1.42814800674

⇒ ab = 28.5629601348   ≈ 28.56 feet