# Stackmat Timer Accuracy/Resolution



## fw (Jan 20, 2011)

Hey guys,

at Aachen Open 2011, we used the stackmat timer to generate random numbers between 0 and 99 (last two digits) to decide who competes in our mystery event. Someone pointed out, that this might not be a uniform random distribution.

I tried to empirically test that thesis by having a look at results in the WCA database. For now, I only used 3x3 results (all, not just best singles or averages), removed all but the last two digits and counted the occurences. I got the following:

[[0, 5061], [1, 1070], [2, 4543], [3, 4672], [4, 485], [5, 4525], [6, 4735], [7, 446], [8, 4515], [9, 4648], [10, 435], [11, 4554], [12, 588], [13, 4473], [14, 423], [15, 4602], [16, 4446], [17, 424], [18, 4872], [19, 4538], [20, 429], [21, 4655], [22, 4444], [23, 410], [24, 453], [25, 4449], [26, 422], [27, 4351], [28, 4741], [29, 440], [30, 4480], [31, 4660], [32, 443], [33, 4615], [34, 4783], [35, 502], [36, 4639], [37, 685], [38, 4395], [39, 565], [40, 4900], [41, 4445], [42, 500], [43, 4700], [44, 4515], [45, 483], [46, 4701], [47, 4485], [48, 459], [49, 564], [50, 4483], [51, 447], [52, 4456], [53, 4841], [54, 515], [55, 4445], [56, 4544], [57, 429], [58, 4483], [59, 4662], [60, 510], [61, 4335], [62, 632], [63, 4423], [64, 455], [65, 4643], [66, 4531], [67, 406], [68, 4799], [69, 4465], [70, 414], [71, 4700], [72, 4530], [73, 442], [74, 489], [75, 4525], [76, 407], [77, 4373], [78, 4648], [79, 418], [80, 4591], [81, 4754], [82, 415], [83, 4526], [84, 4582], [85, 425], [86, 4582], [87, 627], [88, 4510], [89, 391], [90, 4796], [91, 4492], [92, 402], [93, 4772], [94, 4528], [95, 428], [96, 4675], [97, 4446], [98, 441], [99, 518]]

It appears that every third or fourth number is significantly less frequent than the others (which seem to be more or less equally frequent). Does anybody have an explanation for this?

Thanks
Flo


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## jazzthief81 (Jan 20, 2011)

This is a rather well-known issue, but I haven't seen anyone give a reasonable explanation for it. 

For me it seems very hard to explain how the less frequent digits occur as infrequently as they do. The gap is really big.


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## TiLiMayor (Jan 20, 2011)

Remind me of Stefan's QJ timer review. Skip to 2:50


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## Carrot (Jan 20, 2011)

I saw a thread where someone conluded that the stackmat timer only updates itself 60 times a second. But I guess that won't explain this problem :/


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## Bryan (Feb 1, 2011)

Odder said:


> I saw a thread where someone conluded that the stackmat timer only updates itself 60 times a second. But I guess that won't explain this problem :/


 
Say you're on a hundred mile road, and you stop to get out of your car and take a picture by the mile markers. But you only stop 60 times. How many mile markers will have pictures?


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## Bartholomew (Feb 2, 2011)

TiLiMayor said:


> Remind me of Stefan's QJ timer review. Skip to 2:50


 
Nice video man


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## Bartholomew (Feb 2, 2011)

TiLiMayor said:


> Remind me of Stefan's QJ timer review. Skip to 2:50


 
Nice video man i like the way you explain each and every thing about stackmat.


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## TheMachanga (Feb 2, 2011)

I've noticed it's impossible to get 13.37 on a stackmat. I've tried and got 15 13.38's, and 17 13.36's. No 13.37's. Wca also shows no one has ever gotten a 13.37 single.


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## kar0209 (Feb 2, 2011)

TheMachanga said:


> I've noticed it's impossible to get 13.37 on a stackmat. I've tried and got 15 13.38's, and 17 13.36's. No 13.37's. Wca also shows no one has ever gotten a 13.37 single.


This guy has a 13.37 single, but it might me a 11.37 +2.


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## Ara (Feb 6, 2011)

fw said:


> Hey guys,
> 
> at Aachen Open 2011, we used the stackmat timer to generate random numbers between 0 and 99 (last two digits) to decide who competes in our mystery event. Someone pointed out, that this might not be a uniform random distribution.
> 
> ...


 
Cool Manhttp


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## MaeLSTRoM (Feb 6, 2011)

Does this happen on the QJ timer aswell?


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## Lucas Garron (Feb 6, 2011)

MaeLSTRoM said:


> Does this happen on the QJ timer aswell?


No. Did you look through the other 10 posts on this thread?


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## TiLiMayor (Feb 6, 2011)

For those commenting about the video I posted here, credit goes to Stefan, sorry I didn't make it clearer on the post.


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## MaeLSTRoM (Feb 6, 2011)

I did read the other posts but then got confused by the video, sorry.


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