Question

In a test of the effectiveness of garlic for lowering​ cholesterol, 45 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 4.2 and a standard deviation of 19.6.

Answer the following​ (round as​ indicated).

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

The best point estimate is ??? ​mg/dL.

​(Type an integer or a​ decimal.)

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?

What is the confidence interval estimate of the population mean μ​?

?? ​mg/dL < μ < ?? mg/dl

​(Round to two decimal places as ​needed.)

Answer 1

The best point estimate is difference in mean cholesterol levels before and after the treatment=4.2

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?

alpha=0.10

alpha/2=0.10=0.05

df=n-1=45-1=44

t crit in excel

==T.INV(0.05,44)

=1.680229977

90% confidence interval for diff in means

xbar-t*s/sqrt(n),xbar+t*s/sqrt(n)

4.2-1.680229977*19.6/sqrt(45),4.2+1.680229977*19.6/sqrt(45)

-0.7092884, 9.109288

-0.71,9.11

-0.71​ mg/dL < μ < 9.11 mg/dl