A Medical Research Team Is Interested in Determining Whether a New

Multiple Choice

A medical research team is interested in determining whether a new drug has an effect on creatine kinase (CK) , which is often assayed in blood tests as an indicator of myocardial infarction. A random selection of 20 patients from a pool of possible subjects is selected, and each subject is given the medication. The subjects' CK levels are observed initially, after 3 weeks, and again after 6 weeks. The purpose is to study the CK levels over time. Here is a summary of the findings:
In this example, what should we notice?
$$\begin{array} { | c | c | c | } \hline \text { Time (weeks) } & \begin{array} { c } \text { Mean CK Level } \\\text { (U/L) }\end{array} & \text { Standard Deviation (U/L) } \\\hline 0 & 121 & 20.37 \\\hline 3 & 106 & 16.09 \\\hline 6 & 100 & 10.21 \\\hline\end{array}$$

A) The data show very strong evidence of a violation of the assumption that the three populations have the same standard deviation.
B) ANOVA cannot be used on these data because the sample sizes are much too small.
C) The assumption that the data are independent for the three time points is unreasonable because the same subjects were observed each time.
D) There is no reason not to use ANOVA in this situation.