A recent study by researchers at the US Diabetes Research Centre and Oklahoma Un
ID: 3221177 • Letter: A
Question
A recent study by researchers at the US Diabetes Research Centre and Oklahoma University School of Public Health investigated the effects of a mixture of garlic and lemon juice on diabetic patients in the US. A double-blinded, randomized, placebo-controlled trial was conducted with 360 diabetic patients. Randomization was stratified by gender. Patients were randomly assigned to one of four groups. Each group consisted of 45 men and 45 women. The first group was assigned to receive the mixture of garlic and lemon juice daily, the second group was given 20 grams fresh garlic daily, the third group was given 1 tablespoon lemon juice daily, and the last group was not given any intervention. After fifteen weeks of intervention, it was found that the HbA1C (three-month average sugar level) of the combined garlic and lemon juice group was significantly lower compared with the other groups. The researchers also found a greater reduction in BMI, systolic and diastolic blood pressure in the mixed group compared with garlic, lemon juice and control groups. (a) Is this an experimental or observational study? In less than 50 words clearly explain your choice based on the extract given above. (b) For the above study identify, if appropriate, the i) response variable(s). ii) factor and its levels. iii) sample size. (c) Are the four principles of experimental design used in this study? Explain, in the context of the study? (d) Explain explicitly what a confounding variable is. Identify one plausible confounding variable in this study and explain why it is a confounding variable.Explanation / Answer
a) it is an experimental study. Because we are studying the effects of factors on a dependent variable HbA1C levels. In observational study we don't carefully allot samples to each group, we simply observe that group's means and do an exploratory study.
b) Response variable is levels of HbA1C (it will be a number)
Factors are
1) Gender (with 2 levels male and female)
2) Type of trial (with 4 levels - mix of garlic and lime juice, Fresh garlic only, Lime juice only, Nothing)
3) Randomisation - the 360 member group was properly randomised so that experiment is properly structured to 4 groups and within them 2 more groups.
Repetition - There are totally 8 groups. Each group has 45 repetitions. So this condition is also satisfied.
Blocking - to block other variables that influence the treatment. Ideally similar set of diabetic patients should have been used. In this it would have been better if they had informally divided into low diabetic cases and high diabetic cases, and would have assigned to the groups.
Balancing - The experiments are well balanced with 45 per group.
4) confounding variables are uncontrollable variables which interferes with the experiment damaging the experiment and spoiling the results.
One confounding variable could be the level of diabetes levels. The 360 member group can have low diabetes, border level diabetes, very high level diabetes. And this could have interfered with the experiment.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.