Question

In a test of the effectiveness of garlic for lowering​ cholesterol, 47 subjects were treated with garlic in a processed tablet form. Cholesterol levels were measured before and after the treatment. The changes ​(before minus −​after) in their levels of LDL cholesterol​ (in mg/dL) have a mean of 2.8 and a standard deviation of 18.4. Construct a 95​% 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

n=47 ,  c=95%

= 2.8, s= 18.4

formula for confidence interval is

where tc is the t critical value for C= 95% with df= 47-1 = 46

tc= 2.013

2.8 − 5.402 < μ < 2.8 + 5.402

−2.602 < μ <   8.202

Confidence interval is = ( −2.602 , 8.202  )

Conclusion:

The confidence interval limits contain 0, suggesting that the garlic treatment did not affect the LDL cholesterol levels.