Originally Posted by
PlanoFuji
Best efforts have huge variances from test to test and day to day, thereby making the resulting data useless. That is why engineers and scientists design experiments to eliminate (or at least reduce) human subjective effects. Perhaps, you may need a refresher in the mathematics.
I haven't seen the actual study to critique the methodology, but, in general, your concerns can be easily addressed by correctly designing the experiment. For example, treating each day as a separate experimental block allows us to isolate the day to day variance from other, more interesting sources of variance, such as tire size.