Exercises44 er Exercises 41 through 44 refer to a clinical study conducted at th

Question

Exercises44 er Exercises 41 through 44 refer to a clinical study conducted at the Houston Veterans Administration Medical Center on the effec- c? tiveness of knee surgery to cure degenerative arthritis (osteoar- thritis) of the knee. Of the 324 individuals who met the inclusion criteria for the study, 144 declined to participate. The researchers 0 randomly divided the remaining 180 subjects into three groups: ne group received a type of arthroscopic knee surgery called ou debridement; a second group received a type of arthroscopic knee ip surgery called lavage; and a third group received skin incisions to 20 make it look like they had had arthroscopic knee surgery, but no 75 O l actual surgery was performed. The patients in the study did not know which group they were in and in particular did not know if they were receiving the real surgery or simulated surgery. All the patients who participated in the study were evaluated for two years after the procedure. In the two-year follow-up, all three groups said that they had slightly less pain and better knee move- ment, but the "fake" surgery group often reported the best results Source: New England Journal of Medicine, 347, no. 2 (July 11, 2002): 81-88] le 41. (a) Describe as specifically as you can the target popula- tion for this study b) Describe the sample. le y 42. (a) Was the sample chosen by random sampling? Explain. e b Was this study a controlled placebo experiment? Ex- plain. r (c) Describe the treatment group(s) in this study. 43. (a) Could this study be considered a randomized con- trolled study? Explain. Was this Study blind, double blind, or neither? (b) 44. As a result of this study, the Department of Veterans Af fairs issued an advisory to its doctors recommending that they stop using arthroscopic knee surgery for patients suf- fering from osteoarthritis. Do you agree or disagree with ly n the advisory? Explain your answer.

Explanation / Answer

41 a) The target population here is the set of all paitents of degenrative arthiritis. We are seeking a cure to the regenerative arthiritis and hence the target population is the one to which the cure can be provided.

b) The sample ideally would have been a random sample from all paitents having regenrative arthiritis. But actually 324 individuals only met the clinical requirements and out of them only 180 decided to be a part of the experiment. Hence essentially the sample is the pool of 180 individuals who were then subdivided into 3 random classes.

42 a) The sample was not chosen by random sampling. A random samping would have been a random selection from the population of all arthiritis paitents. However the target population was initially shrinked due to clinical requirements to only 324 individuals. It would have been random sampling if a random sample was drawn from 324 individuals. However 144 decided to skip experiment and hence the selection of the remaining 180 is a matter of choice and not a probabilistic selection.

b) This experiment is a controlled placebo experiment because there is a control group which do not receive the surgery, while the two other groups receive the surgery. Hence the other 2 groups are treatment group and the no-surgery group is the control group.

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