Medical: Blood Plasma 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 m 5 7.4 (Reference: The Merck Manual, a commonly used reference in medical schools and nursing programs). 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 3 months. Blood tests showed that x 5 8.1 with sample standard deviation s 51.9.

Use a 5% level of significance to test the claim that the drug has changed (either way) the mean pH level of the blood.

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