Building an experiment (4)
Day to day, symptoms can vary widely depending on a spectrum of inputs — food, sunlight, exercise, socializing, sleep — that have nothing to do with a given treatment. Extending the duration of each treatment block, boosting the number of treatment blocks, or increasing the frequency of reporting means experimenters gather more data. This can negate the effects of non-treatment effects, and boost an experiment’s statistical validity. Every experiment, though, depends on the experimenter’s tolerance for continuing, so most experiment designers compromise on a duration that seems to the person being tested.