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Numbers
12-31-2011, 12:49 AM
Can the math guys out there help me with something? I am looking at the KRach rankings on USCHO and CollegeHockeyNews right now (after all games Friday). All the schools' records match between the 2 sites, but the rating numbers do not.

I don't understand how that can be. Especially since I think I understand the way KRACH works. It makes no sense to me that the iterations can settle to 2 different sets of numbers.

Thanks ahead of time.

Numbers.

Patman
12-31-2011, 01:25 AM
Are you sure they have identical inputs?

Edit: I'd wage it's off SOMEWHERE...

By concavity a solution exists for the maxima and the solution is unique. Another possibility is that they're on different multiplicative scales.

If games are missing/added then most of the ratings should be similar save the mis-inputs... After that I've got nothing

Numbers
12-31-2011, 09:18 AM
Patman,
I thought about this again, and one idea came to mind. Do you know that trick where they add a tie with a team that doesn't exist to everyone's schedule early in the year to make it so that all the teams are connected? Is it possible that one site hasn't deleted that yet?

Patman
12-31-2011, 11:56 AM
Patman,
I thought about this again, and one idea came to mind. Do you know that trick where they add a tie with a team that doesn't exist to everyone's schedule early in the year to make it so that all the teams are connected? Is it possible that one site hasn't deleted that yet?

if so they'd be off all season... I suppose the easiest way to check that... if they print the SOS then, IIRC, the KRACH is equal to

SOS*win%/(1-win%)... if they're putting in the fraction, this is where I'd check

Ed Trefzger
12-31-2011, 03:05 PM
Is it possible that one site hasn't deleted that yet?

Bingo. It's now removed on our calculation. Without the fictitious tie, it can't be calculated until all teams have played.

Craig P.
12-31-2011, 08:46 PM
Patman,
I thought about this again, and one idea came to mind. Do you know that trick where they add a tie with a team that doesn't exist to everyone's schedule early in the year to make it so that all the teams are connected? Is it possible that one site hasn't deleted that yet?
Idle aside: I believe John Whelan has opined that the "best" way to calculate KRACH is with two fictitious games, not just one. It's a statistics thing.