2.75 The article “Tots’ TV-Watching May Spur At-tention Problems” (San Luis Obispo Tribune, April 5,2004) describes a study that appeared in the journal Pediatrics. In this study, researchers looked at records of 2500 children who were participating in a long-term health study. They found that 10% of these children had attention disorders at age 7 and that hours of television watched at age 1 and age 3 was associated with an in- creased risk of having an attention disorder at age 7.
a. Is the study described an observational study or an experiment?
b. Give an example of a potentially confounding vari- able that would make it unwise to draw the conclu- sion that hours of television watched at a young age is the cause of the increased risk of attention disorder.
2.76 A study of more than 50,000 U.S. nurses found that those who drank just one soda or fruit punch a day tended to gain much more weight and had an 80% in- creased risk in developing diabetes compared to those who drank less than one a month. (The Washington Post, Au-gust 25, 2004). “The message is clear. . . . Anyone who cares about their health or the health of their family would not consume these beverages,” said Walter Willett of the Harvard School of Public Health, who helped conduct the study. The sugar and beverage industries said that the study was fundamentally ﬂawed. “These allegations are inﬂammatory. Women who drink a lot of soda may sim- ply have generally unhealthy lifestyles,” said Richard Adamson of the American Beverage Association.
a. Do you think that the study described was an obser- vational study or an experiment?
b. Is it reasonable to conclude that drinking soda or fruit punch causes the observed increased risk of dia- betes? Why or why not?