In a test of the effectiveness of garlic for lowering cholesterol, 42 subjects were treated with garlic in a processed table 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 4.8 and a standard deviation of 16.6.
What is the best point estimate of the population mean net change in LDL cholesterol after the garlic treatment?
Please show all work how you got the answer.