Coffee may not affect blood pressure in women, reported an article in Mobile Register, November 9, 2005. This article was based on a study reported by the Journal of the American Medical Association (2005) that followed 155,594 mostly white female nurses, age 55 on the average, who took part in two long-running health studies. The participants were questioned periodically about their diets and health and followed for over 12 years.

a Is this an observational study or an experiment?

b Caffeine is a well-known beverage in both coffee and cola and has been shown to cause short-term increases in blood pressure. The article reported that drinking coffee doesn't seem to cause long-term high blood pressure. Can such a cause-and-effect conclusion be drawn from this study? Justify your response.

c The study also reported that women in the same study who drank four cans of cola or more each day seem to have a greater risk of high blood pressure. However, researchers cautioned that the study wasn't conclusive because sodium in cola might be a culprit. How would you describe these effects?

d Can these results be applied to all women in the United States? To all U.S. men?