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 (non-radioactive) 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.
Substance type Lifetime
Radioactive 26, 29, 33
Biological 27, 29, 31
Chemical 31, 34, 37
The data are to be analyzed with the Kruskal-Wallis test. Under the null hypothesis that the three populations have the same continuous distribution, then which of following statement is correct
a. None of the three
b. H has approximately an F(2, 6) distribution
c. H has a distribution that cannot be evaluated because the populations may not be Normal
d. H has approximately a chi-square distribution with 3 degrees of freedom