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# Calculating wrong time for 42.195 in race predictor (Read 176 times)

The calculator assumes a small amount of common sense. It probably shouldn't take that for granted.

Runners run.

old woman w/hobby

The calculator assumes a small amount of common sense. It probably shouldn't take that for granted.

steph

"Just stop fucking drinking too much and being fat.  Pretty simple.  Who the hell cares if you like beer.

We can't always do the things we like all the time."  --Candice

You are missing the forest for the trees.

You are also missing some important information that's written in black and white at the bottom of the page: If you enter a second distance, the predictor will automatically make use of this second value to create a personalized coefficient, which will improve the accuracy of the predicted time. You can also type in your own performance factor to adjust the calculation. Typical values are 1.06 to 1.10.

Ah, OK. I  see that I multiplied C instead of elevating (D2/D1) to C... I need glasses. In ain case, the coefficient with my previous example is 0.95. I set the whole thing into an Excel sheet and the results aren't too different from what I calculated by hand, elevating a number to a power by such a value as 0.95 doesn't change it too much.

I assume that C is the value that's set to 1.08 in the formula.

Well, at least I have implemented an excel sheet allowing me to do predictions off line

When I run I feel like a swallow

Because you are free like a bird?

Nope, because of all the flies I eat.

Feeling the growl again

Actually, just looking back at my PR's I've got the exact scenario.

10K on June of this year.  Nice weather, very easy flat course.  Avg pace 7:34.

5 miler in August of this year.  Not terrible weather, but not as nice as June.  Tougher course.  Avg pace 7:39.

I don't feel that I wrongly implemented my race in August.  I didn't do as well as I had hoped, but it just didn't happen that day.

I enter those races into the calculator and it is going to blow up.

You need to use some common sense in using calculators.  I don't understand why you would enter courses run on vastly different terrain, leading to the breakdown of a virtual Law of the Universe --- the further you run, all else equal, the more you slow down -- and expect it to give you meaningful results.

Likewise, if you run a 5K at a certain pace....train for 6 months and get way faster and run a 10K at a better shape....you can't expect the calculator to give you a useful output.  Run a 5K and 10K within a few weeks of each other and use it as intended.

This is not a fault of the calculator, but the user.

"If you want to be a bad a\$s, then do what a bad a\$s does.  There's your pep talk for today.  Go Run." -- Slo_Hand

I am spaniel - Crusher of Treadmills

I didn't enter them into the calculator until this topic came up.  I did and the predictor said I would run a 7:17 pace half marathon.  I'm going to take that to the bank and start out at a 7:15 pace on my next half!    (decided I probably needed to put a wink in there so you guys would know I was joking).

In my example, the courses weren't vastly different, the 5 miler just had some moderate hills, the weather wasn't vastly different, I think the 5 miler was 10 degrees warmer, and the avg pace was only 5 seconds different.  If you didn't think it through, I think you could easily pick up those two races to plug in to the calculator to get a prediction.

All it would take is a little blurb on the predictor page that said that if you enter two runs and the longer run is at a faster pace then it is going to blow up.  Seems like this topic comes up periodically and that would solve it.

Age: 47 Weight: 215 Height: 6'3" (Goal weight 195)

Current PR's:  Mara 3:48:09 (2013); HM 1:36:42 (2015); 10K 43:59 (2014); 5K 21:27 (2013)

Whatever happened to "add 15 sec/mile every time you double the distance" and see if you can beat that prediction.

Options,Account, Forums

Whatever happened to "add 15 sec/mile every time you double the distance" and see if you can beat that prediction.

I can't (esp from marathon to 50mi).

It's a 5k. It hurt like hell...then I tried to pick it up. The end.

I can't either, need more like 30 seconds.  And anyone using a calculator of any kind for Ultras needs an injection of common sense.

Whatever happened to "add 15 sec/mile every time you double the distance" and see if you can beat that prediction.

Nice one!

I'll add it to my sheet.

I'm posting it as soon as I clean it up a bit.

I'm not sure it it makes much sense from the purely athletic point of view... but the algorithms work nicely...

Sometimes I hate being a nerd, LOL

When I run I feel like a swallow

Because you are free like a bird?

Nope, because of all the flies I eat.

an amazing likeness

Come on now...we all know darn well the tool is a mathematical formula designed to give you an indicator.  It has no means to account for whacky input of running race 1 downhill on roller skates, and race 2 uphill on beach sand and then being asked to predict your performance in the Antarctic marathon.

To get reasonable results, the operator should enter reasonable data to feed the prediction math.

Two races of the same distance...wont work.

Two races where the longer is faster...wont work.

Two races of same duration and same distance...wont work.

I've done my best to live the right way. I get up every morning and go to work each day. (for now)

Come on now...we all know darn well the tool is a mathematical formula designed to give you an indicator.  It has no means to account for whacky input of running race 1 downhill on roller skates, and race 2 uphill on beach sand and then being asked to predict your performance in the Antarctic marathon.

To get reasonable results, the operator should enter reasonable data to feed the prediction math.

Two races of the same distance...wont work.

Two races where the longer is faster...wont work.

Two races of same duration and same distance...wont work.

Yeah, running 5 seconds per mile slower on a 5 mile vs. a 10K is the equivalent to going downhill on roller skates and then comparing it to going uphill in beach sand.  Exactly, no exaggeration at all.

I'm just saying that I can see how the original poster could have input times that he felt was reasonable and then received an unexpected unreasonable result.

All that it would take to solve this would be a simple explanatory sentence or two on the calculator page.

Instead every 6 months someone will post on here that the calculator is messed up and all you guys will tell them how dumb they are and that they lack common sense.  If it helps you all sleep at night to ridicule folks, more power to you, keep everything just like it is.

Age: 47 Weight: 215 Height: 6'3" (Goal weight 195)

Current PR's:  Mara 3:48:09 (2013); HM 1:36:42 (2015); 10K 43:59 (2014); 5K 21:27 (2013)

an amazing likeness

Yeah, running 5 seconds per mile slower on a 5 mile vs. a 10K is the equivalent to going downhill on roller skates and then comparing it to going uphill in beach sand.  Exactly, no exaggeration at all.

My apologies. My two outlier made-up examples were not meant to directly relate to your examples and I've removed the quote back to your message to remove that unintended linkage.

I've done my best to live the right way. I get up every morning and go to work each day. (for now)

JimR

I thought Ennay explained it pretty well in the first response.  Either enter the data for one race, or use two very different race distances such as a HM and a 5k.

Yeah we didn't break out our snark bombs until after the math lecture with an incorrect premise.

Runners run.

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