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....

In a test of the effectiveness of garlic for lowering​ cholesterol,

subjects were treated with garlic in a processed tablet form. Cholesterol levels were measured before and after the treatment. The changes in their levels of LDL cholesterol​ (in mg/dL) have a mean of

and a standard deviation of

Complete parts​ (a) and​ (b) below.

a) What is the best point estimate of the population mean net change in LDL cholesterol after the garlic​ treatment?

b) Construct a 90​% 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?