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Many people start their day with a jolt of caffeine from coffee or a soft drink. Most experts agree that people who take in large amounts of caffeine each day may suffer from physical withdrawal symptoms if they stop ingesting

their usual amounts of caffeine. Researchers recruited $11$ volunteers who were caffeine-dependent and who were willing to take part in a caffeine withdrawal experiment. The experiment was conducted on two $2-$day periods that

occurred one week apart. During one of the $2-$day periods, each subject was given a capsule containing the amount of caffeine normally ingested by that subject in one day. During the other study period, the subjects were given placebos. The order in which each subject received the two types of capsules was randomized. The subjects’ diets were restricted during each of the study periods. At the end of each $2-$day study period, subjects were evaluated using a tapping task in which they were instructed to press a button 200 times as fast as they could.

(a) How and why was blocking used in the design of this experiment?

(b) Why did researchers randomize the order in which subjects received the two treatments?

(c) Could this experiment have been carried out in a double-blind manner? Explain.

Step by step solution

01

Part (a) Step 1: Given information

Many people are starting their day by having either caffeine or a cold drink.

02

Part (a) Step 2: Concept

The treatments are randomly assigned to all of the experimental units in a completely randomized design.

03

Part (a) Step 3: Explanation

Many people begin their day with either caffeine or a cool beverage. Researchers agree that those who use significant amounts of caffeine may experience withdrawal symptoms. Various volunteers have been recruited as a result of these efforts. Blocking is the technique of grouping the experimental units into groups that are comparable. Every brick represents one of the persons who will receive therapy. By administering therapies to the subjects, blocking is employed.

04

Part (b) Step 1: Explanation

Because there may be fluctuations in the outcomes and the correct or actual results may not be achieved, orders have been randomized here.

05

Part (c) Step 1: Explanation

If both the researchers and the subjects are unaware of the treatments they are receiving, the survey could be double blind.

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