Track Fairness

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Watch-out-for-that-frog
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Track Fairness

Post by Watch-out-for-that-frog » Wed Feb 14, 2007 2:31 pm

How to tell your track is fair!

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Re: How to tell if you have a "Slow" Lane

Post by DerbyAddict » Wed Feb 14, 2007 4:11 pm

Are our lanes pretty fair?

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Re: How to tell if you have a "Slow" Lane

Post by PWD » Wed Feb 14, 2007 4:25 pm

I would be more curious to see the differences from one lane to another for a single car. Or the average difference for say the top 10 cars.

Our pack race was on a 40' aluminum pianadosi this year. I grabbed the average for the top 12 cars for each lane. Here are the results:

Lane 1 3.008
Lane 2 3.010
Lane 3 3.005
Lane 4 3.003

So the difference from Lane 4 to Lane 2 was .007. Which was the biggest spread.

That is pretty impressive.



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Re: How to tell if you have a "Slow" Lane

Post by DerbyAddict » Wed Feb 14, 2007 11:15 pm

PWD wrote:I would be more curious to see the differences from one lane to another for a single car. Or the average difference for say the top 10 cars.
I would be curious about a single car stats also. Taking the top 10 car averages, while impressive, really just tells us that their average times were close.

However, if you had 2 cars with 10 runs each and the avg times were C1 - 3.0002 and C2 - 3.0004 it would seem to someone from the outside that they were very comparable cars.

But, if C1 had a Std Dev of .0012 and C2 had a Std Dev of .7325 then C1 is actually far and away the better car. By many (scale) miles. And if they met up on C2's "bad" runs, C1 would blow it away. If they met up on C2's good runs, C2 would run away with it.

I know that on my son's car last year (the stats I showed) the Avg time was 3.2724, his max was 3.2984, his min was 3.2377 and his Std Dev was .0154. A very consistent car. The only car to beat him in a race had a Avg of 3.2606 but his max was 3.3546 with a min of 3.2137. His Std Dev was .0405. But he peaked when he needed to, against my son. My son actually beat him two out of three after the racing was over with times still in the 3.2 range.

On our stats from last year, the averages for the top 10 cars are not really meaningful because the competition really dropped off after about number 6. (Hopefully that will change this year after our workshop we held.)

But for that matter, Std Dev is meaningless because of the difference in car design, construction, etc. Of the three best cars with the lowest Std Dev, my son was in the middle. We had .0146, .0154 and .0160. The two bookends averaged more than 2/10s of a second slower than my son. Their min time wasn't even close to my sons avg. So all that showed was they had consistent times for their car.

I guess the only way to really see the consistency or fairness of lanes is to run one car across all lanes in order many times in a controlled environment and get the data that way. It may be something I do over the summer when I can get our meeting hall all day.


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Deltona, FL
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Any day racing PWD is a good day but winning makes a better good day!

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Re: How to tell if you have a "Slow" Lane

Post by tmbnorm » Thu Feb 15, 2007 8:07 am

I agree that it would be best to look at the data from one car, but
we only had 10 rounds of racing. That is only 3 or 4 runs per car per lane.

I studied the data from our Pack Derby. We have a 3 Lane 40' Freedom.
I threw out the values from the first 4 rounds of racing. We eliminated after 4 rounds. There were some cars that did not make it to the end of the track.

The average times for the 3 lanes look like this after that.

Average time for rounds 5 through the finals.

Lane 1
3.215846154
Lane 2
3.21
Lane 3
3.181818182
Rounds 6 through the finals

Lane 1
3.132428571
Lane 2
3.100428571
Lane 3
3.09175


Finals only (I think the cars had started to slow some during the finals)
Lane 1
3.090333333
Lane 2
3.073666667
Lane 3
3.068666667

If you look at the top 3 cars only for the whole race, you get this.

lane 1
3.0798
Lane 2
3.077545455
Lane 3
3.067333333

It is obvious that lane 3 was the fastest and lane 1 the slowest.
Better cleaning of the track should help tighten up the times.



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Re: Track Fairness

Post by gpraceman » Thu Feb 15, 2007 11:33 am

I moved the posts related to statistically determining if averages and standard deviations between lanes are significant to a "sticky" topic.

See http://derbytalk.com/viewtopic.php?t=2479


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