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?
$$\begin{array} { | c | c | c | }
\hline \text { Time (weeks) } & \begin{array} { c }
\text { Mean CK Level } \
\text { (U/L) }
\end{array} & \text { Standard Deviation (U/L) } \
\hline 0 & 121 & 20.37 \
\hline 3 & 106 & 16.09 \
\hline 6 & 100 & 10.21 \
\hline
\end{array}$$

Question

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?
 $$\begin{array} { | c | c | c | } 
\hline \text { Time (weeks) } & \begin{array} { c } 
\text { Mean CK Level } \
\text { (U/L) }
\end{array} & \text { Standard Deviation (U/L) } \
\hline 0 & 121 & 20.37 \
\hline 3 & 106 & 16.09 \
\hline 6 & 100 & 10.21 \
\hline
\end{array}$$

Quizplus · Accepted Answer

The data are not independent across the three time points because they are repeated measures on the same subjects, which violates one of the assumptions of ANOVA that requires independent samples.

A Medical Research Team Is Interested in Determining Whether a New