Another way to help account for those type of issues is to have the test repeated. OVER and OVER and OVER again. I do a lot of research studies for the Air Force Research lab, and I'll often do the same studies 5-15 times, and they'll do their statistics things with all that raw data. It accounts for the newness factor, and also people tend to deviate towards the median over time.
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Calling from deep in the heart, from where the eyes can't see and the ears can't hear, from where the mountain trails end and only love can go... ~~~ Three Rivers Hare Krishna
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