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The following is an excerpt from a paper published in BMJ (formerly the British Medical Journal) in 1994:

Charig et al undertook a historical comparison of success rates in removing kidney stones. Open surgery had a success rate of 78% (273/350) while a minimally invasive procedure called percutaneous nephrolithotomy had a success rate of 83% (289/350), an improvement over the use of open surgery. However, the success rates looked rather different when stone diameter was taken into account. This showed that, for stones of <2 cm, 93% (81/87) of cases of open surgery were successful compared with just 83% (234/270) of cases of percutaneous nephrolithotomy. Likewise, for stones of >/=2 cm, success rates of 73% (192/263) and 69% (55/80) were observed for open surgery and percutaneous nephrolithotomy respectively.

The main reason why the success rate reversed is because the probability of having open surgery or percutaneousnephrolithotomy varied according to the diameter of the stones. In observational (nonrandomized) studiescomparing treatments it is likely that the initial choice of treatment would have been influenced by patients'characteristics such as age or severity of condition; so any difference between treatments could be accounted for bythese original factors. Such a situation may arise when a new treatment is being phased in over time. Randomizedtrials are therefore necessary to demonstrate any treatment effect.

This is an example of Simpson's paradox because:

a. when the lurking variable (size of the stone) is introduced, the conclusions are reversed (percutaneous nephrolithotomy turns out to be less successful at removing them).
b. when the lurking variable (size of the stone) is introduced, the conclusions are reversed (percutaneous nephrolithotomy turns out to be more successful at removing them).
c. when the lurking variable (age or severity of the condition) is introduced, the conclusions are reversed (percutaneous nephrolithotomy turns out to be less successful at removing them).
d. when the lurking variable (age or severity of the condition) is introduced, the conclusions are reversed (percutaneous nephrolithotomy turns out to be more successful at removing them).

Respuesta :

Answer: a. when the lurking variable (size of the stone) is introduced, the conclusions are reversed (percutaneous nephrolithotomy turns out to be less successful at removing them).

Step-by-step explanation: Simpson's Paradox happens when a group of data shows a relationship in each group but it is reversed when the group is combined.

In the BMJ paper, percutaneous nephrolithotomy had a bigger successful rate than open surgery. But, the rates are reversed when the diameter (size) of the stone is included in the research. So, an individual group of data had a relationship and a factor reversed the relationship. This is an example of Simpson's Paradox.

Excerpt form the paper in BMJ.

The excerpt is taken from the paper that got published in the british medical journal of 1994. Ths journal was understand for a historical comparison of the success rates in kidney stone removal. As the success rate of the surgery was about 83%.

Hence the answer is lurking variable is introduced, the conclusions are reversed.

  • As per the excerpt of the Simpsons paradox the  such as rate of 78% and minimal invasive procedure called the percutaneous has a success rate of 83% thus better over open surgery.
  • Thus the option A is correct. The variable size of stone and conclusion was the opposite.

Learn more about the  undertook a historical.

brainly.com/question/12653054.