Chapter 16.1, Problem 1E

Urinary fluoride concentration (in parts per million) was measured for both a sample of livestock that had been grazing in an area previously exposed to fluoride pollution and a similar sample of livestock that had grazed in an unpolluted region.

Do the accompanying data provide evidence that the mean fluoride concentration for livestock grazing in the polluted region is greater than that for livestock grazing in the unpolluted region? Assume that the distributions of urinary fluoride concentration for both grazing areas have the same shape and variability, and use a level 0.05 rank-sum test.