Thread: Decimal places
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Old 04-23-2021, 11:38 AM   #25 (permalink)
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scientifically appropriate

Quote:
Originally Posted by AeroMcAeroFace View Post
Car manufacturers almost always release drag coefficient data rounded to two decimal places, so the 0.31 is actually 0.31 +/- 0.005.

Maximum possible value:
0.315x0.937=0.295155

Minimum possible value:
0.305x0.937=0.285785

The error in the measurements even after the 6.3% drag decrease is thus 0.01, there is no way that 6 decimal places is in any way scientifically appropriate.

It is completely irrelevant whether it is 6%, 6.3% or 6.3000%, the margin of error from the original Cd is way too large to get anything remotely accurate.



I think the people it may offend are scientist and engineers who know the limitations of margin of error.
Probably depends upon the type of science one is doing.
When I'm 'noodling', I simply leave whatever is on the display, or move it into memory, for future re-insertion, for the duration of the calculations.
It would be 'more' work, and less time-efficient to do otherwise. Not to mention accuracy issues.
When I began formal studies, rolling force coefficients for tires easily ran to ten decimal places. Observed wind tunnel values, up to 4-places.
If you're looking for that 0.005 difference from a radiator shutter, you want as 'tight' an accounting as possible.
You know that it requires extremely advanced statistical analysis tools to even identify some 'trends' which are under scientific examination?
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