Question

In a test of the effectiveness of garlic for lowering​ cholesterol, 50 subjects were treated with garlic in a processed tablet form. Cholesterol levels were measured before and after the treatment. The changes ​(beforeminus​after) in their levels of LDL cholesterol​ (in mg/dL) have a mean of 4.8 and a standard deviation of 19.6. Construct a 99​% confidence interval estimate of the mean net change in LDL cholesterol after the garlic treatment. What does the confidence interval suggest about the effectiveness of garlic in reducing LDL​ cholesterol?

Answer 1

x_d = 4.8

s_d = 19.6

The critical t-value for df = 50 - 1 = 49 and is 2.68.

The 99​% confidence interval estimate of the mean net change in LDL cholesterol after the garlic treatment is:

= x_d t*(s_d/n)

= 4.8 2.68*(19.6/50)

= -2.6284, 12.2284

The 99​% confidence interval estimate of the mean net change in LDL cholesterol after the garlic treatment is between -2.6284 and 12.2284.

Since the confidence interval contains 0, we cannot conclude that there is the effectiveness of garlic in reducing LDL​ cholesterol.