07-13-2006, 07:16 AM
An investigator conducts a study to assess the effectiveness of altering school lunches for improving serum lipid concentrations in middle school students. A low fat diet is compared to the standard lunch. In order to minimize changes in the lunch habits of the students who will be given the low fate diet (study group), the lower fat lunch is given to five middle schools on the north side of the city. The control group consists of five schools on the south side of the city where the students will continue to receive the standard lunch. The results indicate that students in the study group have a significant decrease in their average serum cholesterol concentrations compared to the students in the control group who have an average increase in serum cholesterol concentrations. Which of the following raises the most concern about the validity of the study results?
1. Lack of generalizability
2. Lack of placebo
3. others (please specify)
1. Lack of generalizability
2. Lack of placebo
3. others (please specify)