Judging from my experiences, several of these studies may be missing a major confounding factor: the complexity of the problem the code solves. All my longest m

Judging from my experiences, several of these studies may be missing a major confounding factor: the complexity of the problem the code solves. All my longest methods are rather stupid output formatting stuff or if/else cascades that handle tedious by mostly trivial distinctions. But for code that solves hard problems I often write many small functions for independent steps of the solution. So the studies that measure method length/bug count correlation within a single code base or in code written within a single organization might only measure the fact that code that requires no thinking contains fewer bugs than code that does. Paging Captain Obvious. Some of the other studies address that (e.g. Shen 1985 and the code comprehension studies), but as it is so often the case in quantitative studies of things related to programmer productivity, we lack repeated measurments where the only variable is the independent factor whose influence is studied.