The Professor's Response

Hi Professor

I can't seem to get questions #18 on chapter 14 homework. I was wondering if you could help me with the problem, I think I'm doing the ranking portion wrong.

Thanks

See the professor's answer below.

Hi Sandra,

We do not rank the data for the sign test, so if you ranked the data, you are definitely going wrong in that place. All you need to do is to count the number of values below zero and the number above zero, because the claim says the median is equal to zero. S- = the amount of values below zero = 4, and S+ = the amount of values above zero = 11. For a two-tailed test like this one, the test statistic is the larger of these two values (i.e., Max(4,11) = 11). This makes our test statistic equal to 11.

I hope that answers your question,

Professor McGuckian

Hi Sandra,

The claim for the test here is basically the same as the alternative hypothesis. Remember that the Kruskal-Wallis H-test always uses the same null and alternative hypothesis pair:

Ho: The medians are all the same.

Ha: At least two of the medians differ from each other significantly