Computer dealt hands - random?
Hi All
It has been noted by a number of players at the club that we are seeing very unusual numbers of voids in recent weeks. We use a Dealer4 machine/software and have been using this for a number of years now.
Just this week I played on Tuesday afternoon and we only played 21 boards and I had 3 voids and my wife had 1. So, 4 in 21 boards (perhaps there were more in the opposition hands too?). We had 4 voids between us on Wednesday in 24 played boards. Grabbing a random pair from Thursday (I didnt play) and they had 4 voids between them in 24 played boards too!
A quick calculation of the odds:
4 x (39/52 x 38/51 x 37/50 x 36/49 x 35/48 x 34/47 x 33/46 x 32/45 x 31/44 x 30/43 x 29/42 x 28/41 x 27/40) = 0.05116 or roughly 1 in 20 deals.
So, on average we should be seeing about 1 to 2 per night, whereas in 69 boards over the last 3 days we have seen 12 voids (possibly more?), or more than 1 in 6 deals.
Incase this is just an unusual series of deals (it is only 1 in 20 on average so outliers are expected and normal), I have looked back on previous nights and I am seeing similar numbers, 3 and 4 voids each session for the last few weeks.
Has anyone had any experience of this sort of thing and have any recommendations? I am thinking that perhaps an uninstall/reinstall of software might be in order.
Comments
Big Deal software is free and universally respected for this. The WBF, EBL & EBU all use it.
https://sater.home.xs4all.nl/doc.html
I think that Big Deal is included in Dealer4... though I am not sure that it is included in the version we have.
I will have a look next time I'm at the club and update to the latest version if not.
Thank you
It may be that they have included more than one option with regard to which software you can use, so worth checking which one has been selected. Also worth checking that no-one has fiddled with the settings and asked it to produce deals that are other than random!
I dont think that there are any options for non-random, or give crazy distributions, but I will have a look. I dont have access to the software just now, but i have had a look at the manual.
Your 1 in 20 calculation is for a single hand, so you shouldn't add your wife's voids to your total. The probability of there being one or more voids in a deal is closer to 1 in 5.
@michael, you are right of course, the 1 in 20 is for a single hand, but the hands in a full 52 card deal are not mutually exclusive and so do impact the odds of each other hand.
Perhaps it is closer to 1 in 5 (my feeling is that it would be a little less due to each hand shape impacting the possible shapes and thus the odds of certain shapes).
I have had a further look and as we dont often run Mitchel movements, it took me a little while to collect a few nights with this movement - what I found was this (number of voids for all hands/directions in the number of boards played):
10 in 30
7 in 27
5 in 28
9 in 24
So, whilst not a statistically significant number of nights, this comes out at a void every 3.5 hands.
It just does not seem right.
I will be having a look at the version of the software that we are using and will update if needs be so that we use Big Deal for hand creation.
Thanks
Surely you should be looking at all the boards in the deal files for those nights not just the (non-random) sub-set you (the club) happened to play. Some dealing programs keep internal statistics for all the deals they have generated.
I always get accused of pressing the "interesting button" whenever anyone encounters 2 or 3 7-card suits in a night or someone bids a speculative (making) slam against them. I use DealMaster Pro in batch mode mostly; BigDeal for one-off tournaments.
Peter
Thanks Peter
I will have a look when I am at the club tomorrow
okay, had a look through the Dealer4 software and we didn't have the latest version, so this has been updated and we are now using the Big Deal (now integrated into the dealing software) to create the random hands.
The software does not keep running statistics of the dealt hands, but I have looked through some historical deals and checked the stats for those... due to the small number of hands dealt (generally 25 - 33 hands) it is not easy to get anything significant from that.
However, I have seen a few deals where the number of voids is exactly the number expected and I have seen some with 75% more voids than average (though I only looked at about 10 deals, I never saw any with fewer than expected).
It does seem that voids are considerably more likely that I intuited (goes to show how bad people are at guessing probabilities) and following discussions at the club, everyone guesses around 1 or maybe 2 voids in a night of 27 boards, where this is more likely to be in the range of 4-6 voids in the deal.
I will be keeping a small eye on things now that we have Big Deal to see if there is any difference.
Martin, I just looked through a couple of my recent batch dealing files - 39 sessions for a total of 1,116 boards (= 4,464 hands). The hand records have summary boxes for the number of voids and 7+ card suits amongst other things. There were at total of 246 voids and 167 7+ card suits. Wikipedia has the probabilities of voids at 5.12% and 7+ card suits at 4.04%. So, over my 1,116 boards / 4,464 hands, I expect to see: 228 voids and 180 7+ card suits.
I'm quite happy with these numbers ... there is no "interesting" button!
Peter
I use Dealmaster Pro 6.0 (this is the latest version; last updated September 2014) in batch mode.