Thanks seifrob!
I'll describe/quote the main parts of the test you linked (
http://s89686473.onlinehome.us/airtabs-test.html ), for posterity (these things have a bad habit of disappearing from the web):
Date posted: 2007
Vehicle: Honda Fit
VG's used: AirTabs
Methodology: coastdown test, 100-80 km/h, on a nearly level road, by dipping the clutch at 100 km/h, manually starting a timer, then stopping the timer @ 80 km/h. Baseline (no VG's); then 8 VG's across the end of the roof; then baseline repeated; then 8 VG's across the roof + 4 VG's on each side.
Results: (time in hundredths of seconds)
A1 (baseline, no VG's): 1550, 1647, 1607
B1 (8 VG's taped to roof): 1691, 1678, 1700, 1706
A2 (baseline, no airtabs): 1628, 1623, 1649
B2 (8 VG's taped to roof, plus 4 taped on each side): 1597, 1662, 1722, 1671
16.17 seconds: average time of the "A" runs coasting from 100 - 80 km/h.
16.78 seconds: average time of the "B" runs coasting from 100 - 80 km/h.
00.61 seconds: difference
Experimenter's conclusion & comments:
Quote:
Overall, the average time (in hundredths of a second) for both sets of test runs with Airtabs was 1678, 3.77% greater than the average times for the unmodified car of 1617. Seemingly not a huge difference, but it is very much statistically significant, according to this web t-test calculator, which claims that the probability of this event, assuming the null hypothesis, is 0.011.
The first run in set B2 was anomalously slow. I suspect this could be the result of the car cooling down (most importantly, I guess, the tires) while I took my time taping the Airtabs back on. Also, it started raining very lightly during the last run, again putting the Airtabs at a disadvantage.
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