State the null hypothesis tested by the Kruskal–Wallis procedure.

Exercise 13.9 Antipyretics trial. A trial evaluated the fever-reducing effects of three substances. Study subjects were adults seen in an emergency room with diagnoses of flu with body temperatures between 100.0 and 100.9°F. The three treatments (aspirin, ibuprofen, and acetaminophen) were assigned randomly to study subjects. Body temperatures were reevaluated 2 hours after administration of treatments. Table