Question: Let x be a random variable that represents the pH of arterial plasma (i.e. acidity of the blood). For healthy adults, the mean of the x distribution is \[\mu \] =7.4. (Reference: Merck Manual). A new drug for arthritis has been developed, however, it is thought that this drug may change blood pH. A random sample of 31 patients with arthritis took the drug for three months. Blood tests showed the average pH to be \[\overline{x}\] = 8.1 with sample standard deviation s = 1.9. Use a 5% level of significance to test the claim that the drug has changed (either way) the mean pH level of the blood.