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 4.1and a standard deviation of 16.3 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?

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

____ mg/dL < μ < ____ mg/dL

Answer 1

df = n - 1 = 50 - 1 = 49

From T table,

t critical value at 0.01 sgnificance level with 49 df = 2.68

99% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

4.1 - 2.68 * 16.3 / sqrt(50) < < 4.1 + 2.68 * 16.3 / sqrt(50)

-2.08 < < 10.28

Since 0 contained in confidence interval, garlic in reducing LDL cholesterol is not effective.