Question

Two studies are run to measure the extent to which taking zinc lozenges helps to shorten the duration of the common cold. Researchers in the first study send questionnaires to all 5000 employees of a major teaching hospital asking whether they have taken zinc lozenges to fight the common cold and what they perceive to be the benefits, if any. The response rate is 90%. The 500 people who did not respond to the first mailing receive follow-up telephone calls, and eventually responses are obtained from over 99% of the hospital employees. Researchers in the second study take a group of 100 volunteers and randomly select 50 to receive zinc lozenges while the others receive a similar-looking, similar-tasting placebo. The volunteers are not told whether they are taking the zinc lozenges, but their doctors know and are asked to accurately measure the duration of common cold symptoms experienced by the volunteers. Comment on the designs of the two studies, remarking on their good points and on possible sources of error.

Answer 1

The first study relied on self-reporting and subjective perceptions, while the second study was a randomized controlled trial with more reliable data. Possible errors in the first study include self-reporting biases, while errors in the second study can include the placebo effect.

Step-by-step explanation:

The first study inquired about zinc lozenge usage and its perceived benefits in fighting the common cold among 5000 hospital employees. The response rate was 90%, and those who didn't respond initially were followed up with telephone calls to achieve a 99% response rate. However, this study relies on self-reporting and subjective perceptions, which can introduce bias. The second study involved randomly selecting 50 out of 100 volunteers to receive zinc lozenges while the others received a placebo. The duration of common cold symptoms was accurately measured by the volunteers' doctors. This study is a randomized controlled trial that reduces bias and provides more reliable data. Possible sources of error in the first study include self-reporting biases, inaccurate perceptions, and the reliance on employee responses. In the second study, possible sources of error include the placebo effect and the potential for doctors to influence the reported duration of symptoms.