A Researcher Is Interested in the Survival Times of a Particular

Multiple Choice

A researcher is interested in the survival times of a particular organism after it is subjected to three substances. The first is a radioactive material, the second is a biological material, and the third is a chemical (nonradioactive) substance. Organisms are brought into contact with each of the three substances to see how long they will last (in hours) until they die. The times are recorded for each substance used in the study, and the results are given below:
$$\begin{array} { | l | l | } \hline \text { Substance type } & \text { Lifetime } \\\hline \text { Radioactive } & 26,29,33 \\\hline \text { Biological } & 27,29,31 \\\hline \text { Chemical } & 31,34,37 \\\hline\end{array}$$ The data are to be analyzed with the Kruskal-Wallis test. The null hypothesis is that the time until death has the same distribution in all groups. What is the alternative hypothesis?

A) Not all three mean lifetimes are equal.
B) The mean time until death is longer for one substance than for the other two substances.
C) The mean lifetimes are not Normally distributed in each group.
D) None of these choices are correct.