A doctor is in the habit of measuring blood pressures twice. She notices that patients who are unusually high on the first reading tend to have somewhat lower second readings. She concludes that patients are more relaxed on the second reading. A colleague disagrees, pointing out that the patients who are unusually low on the first reading tend to have somewhat higher second read-

ings, suggesting they get more nervous. Which doctor is right? Or perhaps both are wrong? Explain briefly. PL968