In an Experiment on the Effect of Garlic on Blood

Multiple Choice

In an experiment on the effect of garlic on blood lipid concentrations, adult volunteers with slightly elevated cholesterol levels were randomly assigned to one of four treatments taken daily for six months: raw garlic, garlic powder, garlic extract, or a placebo. The participants' LDL levels (low-density lipoprotein, or "bad" cholesterol, in mg/dL) were assessed at the end of the six-month study period. Summary statistics and a partial ANOVA table for this study are shown here.

$\begin{array} { l c c c } \text { Treatment } & \text { Mean } & \text { Standard Deviation } & \text { Sample Size } n \\\text { Raw garlic } & 142 & 22 & 49 \\\text { Garlic powder } & 137 & 25 & 47 \\\text { Garlic extract } & 137 & 22 & 48 \\\text { Placebo } & 133 & 21 & 48\end{array}$

$$\begin{array}{l}\begin{array} { l l r } \text {Source }&\text {df }&\text {Sums of Squares }&\text {Mean Square }&\text {F-Ratio }\\\text { Treatment}&&&659.46\\\text {Error }&&95,457.00\end{array}\end{array}$$
The research question is: Do the data provide evidence that the treatments affect the mean LDL level in this population? What is the degrees of freedom in the numerator for this test?

A) 3
B) 4
C) 6
D) 46