Describe the source of variation which may occur in medicine and how they can affect clinical findings. Secondly, discuss the various types of variables found in biostatistics and how they affect data interpretation.
I found an interesting article that discusses differences in physician adherence to clinical guidelines based on patient characteristic:
J Gen Intern Med. 2007 March; 22(3): 289-296.
Published online 2007 January 9. doi: 10.1007/s11606-006-0075-2
Sources of Variation in Physician Adherence with Clinical Guidelines: Results from a Factorial Experiment
J. B. McKinlay,corresponding author1,3 C. L. Link,1 K. M. Freund,2 L. D. Marceau,1 A. ...
This solution provides a reference for expanding the topic question and a brief overview of a type of variation that might occur in medical practice, along with a description of variables and how they can affect research.