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Chapter 2: Problem 46

An experiment to evaluate whether vitamins can help prevent recurrence of blocked arteries in patients who have had surgery to clear blocked arteries was described in the article "Vitamins Found to Help Prevent Blocked Arteries" (Associated Press, September 1, 2002). The study involved 205 patients who were given either a treatment consisting of a combination of folic acid, vitamin B 12, and vitamin B6 or a placebo for 6 months. a. Explain why a placebo group was used in this experiment. b. Explain why it would be important for the researchers to have assigned the 205 subjects to the two groups (vitamin and placebo) at random. c. Do you think it is appropriate to generalize the results of this experiment to the population of all patients who have undergone surgery to clear blocked arteries? Explain.

Short Answer

Expert verified
a. A placebo group was used in the experiment to serve as a control group and to isolate the therapeutic effects of the vitamins treatment. b. Random assignment to the two groups was important to eliminate any systematic bias and to ensure that any difference in the outcome was due to the treatment only. c. When it comes to generalization, it requires careful consideration of the sample size and the demographics of the sampled patients. This is because for valid generalization, the sample should be representative of the entire population.

Step by step solution

01

Understanding the usage of placebo

A placebo group is used in an experiment to serve as a control group. Placebo is a substance with no therapeutic effect and is provided to patients in the control group. This is to check whether the observed effects in the experiment are due to the vitamins treatment or due to other factors including psychological effects like placebo effect where the patient feels better because they think they are getting treatment.
02

Understanding random assignment

Random assignment of the subjects to the different groups is important to eliminate any systematic bias. It ensures that any other effect except the treatment would be evenly distributed among the two groups, thus any difference in the outcome would be due to the treatment only.
03

Assessing generalization of results

To generalize the results of the experiment to the entire population of all patients who have undergone surgery to clear blocked arteries would require careful consideration of the sample size used in the experiment and the demographic similarities between the sample and the wider population. In this case, the study only consists of 205 patients. For a more reliable generalisation, the study should be replicated with larger and more diverse samples to ensure it is representative of the entire population.

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