Question

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

4848

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

4.14.1

and a standard deviation of

17.817.8.

Construct a

9595​%

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?Click here to view a t distribution table.

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Click here to view page 1 of the standard normal distribution table.

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Click here to view page 2 of the standard normal distribution table.

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What is the confidence interval estimate of the population mean

muμ​?

negative 1.07−1.07

​mg/dLless than<muμless than<9.279.27

​mg/dL

Answer 1

t critical value at 0.05 with 47 df = 2.012

95% confidence interval for is

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

4.1 - 2.012 * 17.8 / sqrt(48) < < 4.1 + 2.012 * 17.8 / sqrt(48)

-1.07 < < 9.27

Since 0 contained in this confidence interval, the garlic for lowering cholesterol test is not effective.