A medical researcher treats 200 subjects with high cholesterol with a new drug.
ID: 3112586 • Letter: A
Question
A medical researcher treats 200 subjects with high cholesterol with a new drug. The average decrease in cholesterol level is = 90 after two months of talking the drug. Suppose you construct a 93% confidence interval. Which of the following would produce a confidence interval with a smaller width (shorter interval or smaller margin of error) than the 93% confidence interval? A) Give the drug to 500 subjects rather than 200. B) Give the drug to only 100 subjects rather than 200, since 100 people are to manage and control. C) Compute a 99% confidence interval rather than a 93% confidence internal. D) none of the above.Explanation / Answer
A 93% confidence interval means that there is 93% probability that the interval covers the population parameter. Therefore, a 99% confidence interval means that there is 99% probability that the interval covers the population parameter.
Hence, in case of 99% confidence interval there is more chance to make less error.
The dependency of confidence interval with width is as summarized below:
(1) The width of the confidence interval decreases as the sample size increases.
(2) The width increases as the standard deviation increases.
(3) The width increases as the confidence level increases (0.5 towards 0.99999 - stronger).
(4) The width increases as the significance level decreases (0.5 towards 0.00000...01 - stronger).
On the basis of above discussion, the option (A) is correct.
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