In an experiment to study the way in which different anesthetics affected plasma epineph...

In an experiment to study the way in which different anesthetics affected plasma epinephrine concentration, 10 dogs were selected and concentration was measured while they were under the influence of the anesthetics isoflurane and halothane (“Sympathoadrenal and Hemodynamic Effects of Isoflurane, Halothane, and Cyclopropane in Dogs” Anesthesiology [1974]: 465–470). The resulting data are as follows.

Use a level .05 signed-rank test to see whether the mean epinephrine concentration differs for the two anesthetics. What assumption must be made about the epinephrine concentration distributions?