Electrical Measurements of Nerve Activity Give a Clue to the Nature

Multiple Choice

Electrical measurements of nerve activity give a clue to the nature of poisoning with the insecticide DDT. When a nerve is stimulated, its electrical response shows a sharp spike, which is followed by a much smaller second spike. In a randomized experiment, researchers measured the relative height of the second spike as a percent of the first spike, comparing six rats poisoned with DDT and a control group of six unpoisoned rats. Here are the findings: $$\begin{array} {| l | l l l l l l |} \hline \text { Poisoned } & 8.456 & 12.207 & 16.869 & 20.589 & 22.429 & 25.050 \\\hline \text { Unpoisoned } & 6.642 & 8.182 & 9.351 & 9.686 & 11.074 & 12.064 \\\hline\end{array}$$
Let W, the Wilcoxon rank sum test statistic, be the sum of the ranks assigned to the relative spike height in rats poisoned with DDT.
The researcher is interested in testing the following two-sided test:
H₁: No difference in distribution of relative spike heights.
H_a: One of the conditions produces relative spike heights that tend to be larger.
What is the P-value for the test?

A) Less than 0.01
B) Between 0.01 and 0.05
C) Between 0.05 and 0.10
D) Greater than 0.10