Quote:
Originally Posted by CapriRacer
It is true that the presentation doesn't say larger = better, and it is also true that I have drawn that conculusion, but I am not the only person to have done so.
|
Many people thought the world was flat!
It's probably true that, all things being equal, a wheel with a larger radius tire will have slightly less rolling resistance due to less bearing drag, but there's no restriction that all things be equal in tire construction, so stating bigger = better is too broad a statement to make given the data. The safest thing to say would be that the tire w/ the lowest RRC is the best one in the context of rolling resistance.
Quote:
Originally Posted by CapriRacer
True - and perhaps I've overstated this. However, I think it is painfully obvious that larger sized tires give better RRC values than smaller sized tires - and if that were wrong, I feel confident someone would have pointed this out, particularly considering that there are regulations being written and this would be a very important thing to get right.
|
It's a bit too general. It's true that for Goodyear Integrity tires, excluding most 16 inchers and all 17 inch tires, larger sizes tend to have better RRCs, but that's way more restricted than any statement you've made.
Quote:
Originally Posted by CapriRacer
But the data IS representative. They are all the same make and model - and you don't have to have EVERY data point to draw a conclusion.
But you are right to point out that there are risks associated with extrapolating data.
Side note: The way science works is that a phenomenon is observed and reported and some conclusions are drawn from those observations - just like I did. Then the data is examined, the analysis critiqued, other studies run, etc. - all with the idea of trying to refute the conclusion. If the conclusion stands up to scrutiny, then it is accepted - until further data comes along. We are in the critique phase - and I have no problem with anyone critiquing, questioning, etc.
|
You don't need any data to draw a conclusion!
However for a regression analysis the sample needs to be representative of the population for the inference prediction. If a lot of 16" tires and all of the 17" tires are excluded, then you can't include those larger tires in any statement made, and you would be restricted to a statement about most Goodyear Integrity tires less than 16 inches. Science works because the people that draw conclusions also test those conclusions. You drew the conclusion that bigger = better, so in order for it to be scientific you would need to test it rigorously, not just cite data on one tire brand/type that excludes some of the larger sizes. Citing the data is sufficient for a hypothesis, essentially an educated WAG, but the scientific method is more than just a hypothesis.