Question

What's wrong with each of these study designs, given the hypothesis? why is the study design inappropriate for testing the stated hypthesis? Hypothesis: Fruits and vegetables reduce the risk of heart disease. Study Design: ​45.000 italians will be interviewed about their diet and then followed for 10 years. At the end of that time, the number of coronary events will be assessed and statistical analysis will be used to determine if those who ate more fruits and vegetables were less likely to have heart disease.

Answer 1

A study design must fulfill some criteria to be technically complete and scientifically sound. According to the information, a study was designed to check the hypothesis whether fruits and vegetables reduce the risk of heart disease. However, this study design has following flaws:

1. The sample size is too low to statistically examine the hypothesis.
2. The control groups, i.e. a negative control and a positive control group is missing from the experiment.
3. Since it represents a clinical study, a placebo-treated group too must be included in this study.
4. It is highly important to control or at least monitor the eating habits of the subjects since the effect of their diet is being investigated on heart disease.

Thus, these points must be incorporated in the study.