All of science is just a sample. Population trends can be observed in smaller subsets.

There are excuses that are perfectly reasonable to go over by 1 mph. Speedometers are not perfect, and neither are radar detectors. All my cop friends have told me they are trained to give 10% of the speed to normal variation, so at 50mph you would be within the limit to go 55. This has been my personal experience while driving too.