Question

The study problems below have a threat to the validity of their results. Match up the most likely errors below to the studies indicated below.

Potential errors:

a) Confounding

b) Selection bias

c) Random sampling error

d) Information bias

Studies:

1. To test whether persons exposed to pesticides during early childhood were more likely to develop neurological problems, a case-control study was designed. The results were significant. Both cases and controls (age range: 45-85) were asked detailed questions about their pesticide exposure during early childhood.

2. An epidemiologist examines the association between the use of diet pills and migraine using a case-control study design. Her subjects are outpatients from a large community hospital. She finds that those using pills are more likely to complain of migraine, but she also discovers that those who have migraine and use diet pills are more likely to be referred to the hospital than those who have migraine but are not using diet pills.

3. The authors of a cross-sectional study hypothesized that lack of regular exercise is associated with obesity in children. In the study of 12 children, however, they failed to show a statistically significant association between exercise habits and obesity (RR=1.9; 95% CI=0.7-14.3)

4.A large epidemiological study found that older adults with dementia were more likely to develop liver cirrhosis than those without dementia. The investigators, however, could offer no plausible biological explanations. Many of the subject reported heavy drinking.

Answer 1