DrVirgo
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18. 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-fat 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?
A) Biased measurement
B) Lack of generalizability
C) Lack of a placebo
D) Lack of randomization
E) Low power
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| endocrine
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a?
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| sarika
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c
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| sobia naeem
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d.
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| mazinger
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I think its d
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original mazinger z
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| robin082006
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D is most suitable because in this study two study groups were chosen from different area.
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| jagian75
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why not a becoz its not a double blinded study the researches are going to expect a decrease in the lipid levels. why not A . can someone please explain?
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| tolito
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i think it is D. cos there was no random selection of the schools. there may be some confounding factors responsible for the difference between north and south.
A may not be right because the lipid value is a lab analysis which neither the investigator nor the subject can change or affect.
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| pearljam59
Forum Guru
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I believe D.
This is a COHORT study; an observational study as subjects are followed over time for development of disease.
According to QBANK, the most COMMON bias in this type of study is selection/sampling bias which is the NONRANDOM assignment to study groups.
FYI the most common bias for a case control study is recall bias.
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| guest007
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its D
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| netlover
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D for sure
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| nadiabarati
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D
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