Question

7. Lipitor is a cholesterol-lowering drug made by Pfizer. In Collaborative Atorvastatin Diabetes Study (CARDS), the effect of Lipitor on cardiovascular disease was assessed in 2838 subjects aged 40 to 75, with type-2 diabetes, without prior history of cardio- vascular disease. In this placebo-controlled, double-blind experiment, subjects were randomly allocated to either Lipitor 10 mg daily (1428) or placebo (1410) and were followed for 4 years. The response variable was the occurrence of any major cardiovas- cular event.

1. (a) What type of experimental design is this? (Is it completely randomized or matched-pairs?)

2. (b) What does it mean for the study to be double-blind?

3. (c) What is the population for which this study applies?

4. (d) What is the sample?

5. (e) What are the treatments?

6. (f) What is the response variable? Is the response variable qualitative or quantita- tive?

Answer 1

(a). The given experiment is a completely randomized design because the subject in this experiment are assigned the treatments randomly. On the other hand in case of matched pair design, the subject are grouped into pairs on some common basis and then one person in the pair is given one type of treatment and another receives another treatment.

b). A blind study is one in which the subjects do not know what treatment they are receiving. In a double blind study the researcher also is not aware about which group of people are recieving which treatment. This is done so as to ensure that results are not affected by any subjectivity.

(c). The population in this study are the people aged between 40 to 75 years who have type 2 diabetes.

(d). The sample consists of 2838 people between 40 to 75 years and having Type 2 diabetes without any history of cardio vascular diseases. They were followed for 4 years after giving treatments.

(e). There are 2 treatments in the study. The first one is Lipitor 10 mg which is given to 1428 subjects and other is placebo given to 1410 subjects.

(f). The response variable in this study was the occurrence of any major cardiovascular event within 4 years of observation. This response variable is quantitative in nature as there can be a cardiovascular event or not. It can be measured in terms of numbers.