Researchers Examined a New Treatment for Advanced Ovarian Cancer in a Mouse

Multiple Choice

Researchers examined a new treatment for advanced ovarian cancer in a mouse model. They created a nanoparticle-based delivery system for a suicide-gene therapy to be delivered directly to the tumor cells. The mice were randomly assigned to have their tumors injected with either the gene -- nanoparticle combination, the gene alone, or some buffer solution (placebo) . The following table shows the tumor fold-increases after two weeks in a total of 29 mice. A fold-increase of 1 represents no change; a fold-increase of 2 represents a doubling in volume of the tumor.
$$\begin{array} { | c | c | c | } \hline \text { Buffer } & \text { Gene } & \text { Gene+Nano } \\\hline 3.3 & 2.7 & 1.1 \\3.8 & 3.0 & 1.1 \\4.1 & 3.3 & 1.2 \\5.4 & 3.4 & 1.4 \\5.4 & 3.9 & 1.8 \\6.8 & 4.3 & 1.8 \\7.0 & 5.3 & 2.1 \\7.8 & 5.6 & 2.1 \\8.1 & 5.6 & 3.5 \\9.1 & & 4.1 \\\hline\end{array}$$ We choose to analyze these data with the Kruskal-Wallis test. The null hypothesis is that tumor fold-increase has the same distribution in all groups. What is the alternative hypothesis?

A) Not all three mean tumor fold-increases are equal.
B) The mean tumor fold-increase is larger for one treatment than for the other two treatments.
C) The mean tumor fold-increases are not Normally distributed in each group.
D) The tumor fold-increases are systematically larger in some treatments than in others.