The second largest problem in epidemiology

Having identified earlier the largest problem in epidemiology I trying now to identify the second most relevant problem. Hopefully I can do it by just one sentence:
“There is an inherent discrepancy to be as exact as possible when describing empirical data by figures, tables and models but to be as creative, uncoupled, associative and visionary when it comes to the interpretation and discussion of empirical data.”
Look at any paper in “Epidemiology” and decide where they score…