Hmmn. Spent the last day reading up on stats - great way to pass the time :blink:
In any experiment there are 2 possible types of error: systematic and random.
Ergomo isn't factory calibrated properly
Offset is incorrect for temperature
k- factor in Ergomo is incorrect
Systematic errors affect all samples collected.
This run had more/less wind than that run
Goofy couldn't hold his aero position in this run or that run
Height up or down the bank was not constant
Too close behind another cyclist on the track and run was draft affected
Temperature varies between trials
Left/Right leg imbalance changes total reported watts
Random errors affect some samples collected.
Because the systematic errors affect everything the same way, we can probably discard them if we are only looking to show a significant difference between 1 helmet and another. In this case systematic errors might be important if we really want to know the difference at [i]exactly 200 real watts[/i], not what the test Ergomo unit reports as 200 watts.
Random errors are much more sinister. Maybe the difference between 2 helmets is due to solely random error, and not because 1 is more aero than another. This we don't want.
Still thinking ...