Question

1. The theory of atherosclerosis (hardening and narrowing of the arteries) emphasizes the role of inflammation in the vascular walls. Because ibuprofen is known to possess a wide range of anti-inflammatory actions, it was hypothesized that it might help in the prevention of atherosclerotic lesion development. Both a low-cholesterol and a high-cholesterol diet were used, as the extent of atherosclerosis is also affected by diet. Sixteen New Zealand rabbits served as subjects in the experiment and, after three months, the percentage of the surface covered by atherosclerotic plaques in a region of the aorta was evaluated. Although ibuprofen did suppress the expression of a gene thought to be related to atherosclerosis, it was not shown to have an effect on the extent of fat-induced atherosclerotic lesions.
   1. a) What are the individuals in this experiment?
   2. b) What is the response variable in this experiment?
   3. c) List the explanatory variable(s) in this experiment.
   4. d) How many treatments are there in this experiment? Complete an appropriate table that shows the treatment set up.
   5. e) Using the specific information given in the scenario and the treatments you identified in part (d), sketch a diagram to show a completely randomized design for this experiment (but don’t do the randomization).
   6. f) Should we consider any level of blinding in this experiment?

Answer 1

a) The individual in this experiments are Sixteen New Zealand rabbits which served as subjects

b) The response variable in this experiment is atherosclerotic lesion development

c) The explanatory variables are type of diet given to 16 New Zealand rabbits with two levels one with 8 randomly allocated rabbits with low-cholesterol diet and the other with remaining 8 rabbits with high-cholesterol diet

d) There are two treatments in the experiment with 1) Ibuprufen treatment for 8 rabbits fed with low-cholesterol diet 2) Ibuprufen treatment for remaining 8 rabbits fed with high-cholesterol diet to compare the results on the extent of fat induced altherosclerotic lesion development

e)Diagram showing completely randomized design of treatment are shown as below

  f) Single blinding shall be considered at the receiving end of evaluators  who test Ibuprufen treatment by not letting knowing them of which rabbits are fed with low or high cholesterol diet in the experiment