Question

1. A recent study on the effect of raw garlic on plasma lipid concentration in adults with moderate hypercholesterolemia was conducted using 49 randomly selected subjects treated with raw garlic and 48 randomly selected subjects with a placebo.

The 49 subjects treated with raw garlic had LDL cholesterol measurements with a mean of 151 and a standard deviation of 15, while 48 subjects given placebos had LDL cholesterol measurements with a mean of 149 and a standard deviation of 14.

Use a 0.05 significance level to test the claim that there is no difference between the mean LDL cholesterol levels of subjects treated with raw garlic and subjects given placebos.

1. Check requirements first.
2. If requirements are met, list each of the 8 steps in a hypothesis test to test the claim. Remember at Step 5 to write down the StatCrunch method you use.

Answer 1

In order to run an independent t-test, we need the following:

• One independent, categorical variable that has two levels/groups.
• One continuous dependent variable.

The requirements are met.

The hypothesis being tested is:

H0: µ1 = µ2

H1: µ1 ≠ µ2

raw garlic	placebo
151	149	mean
15	14	std. dev.
49	48	n
	95	df
	2.000	difference (raw garlic - placebo)
	210.653	pooled variance
	14.514	pooled std. dev.
	2.947	standard error of difference
	0	hypothesized difference
	0.679	t
	.4991	p-value (two-tailed)

The p-value is 0.4991.

Since the p-value (0.4991) is greater than the significance level (0.05), we cannot reject the null hypothesis.

Therefore, we can conclude that there is no difference between the mean LDL cholesterol levels of subjects treated with raw garlic and subjects given placebos.