Mikes10 Posted September 13, 2013 Share Posted September 13, 2013 The BBC and maths Professor Marcus du Sautoy explain how changing your mind in an apparently 50/50 gamble can improve your chances of winning. The problem is based on a 1970s American game show, and demonstrates not everything is as it seems. If you thing about it too long then you begin to doubt your own reasoning. Follow the link: http://www.bbc.co.uk/news/magazine-24045598 Link to comment Share on other sites More sharing options...
geared Posted September 13, 2013 Share Posted September 13, 2013 ah thats really quite clever. Link to comment Share on other sites More sharing options...
Brentner Posted September 13, 2013 Share Posted September 13, 2013 I've heard of this before, and it still confuses me... In a way it makes total sense, but there's still this nagging thought that something isn't right! Link to comment Share on other sites More sharing options...
Happ Hazzard Posted September 13, 2013 Share Posted September 13, 2013 It really isn't that hard to understand. You have a 2/3 chance of picking a goat at the start, and if you pick a goat, switching will always get you the car. Link to comment Share on other sites More sharing options...
*_ash_* Posted September 13, 2013 Share Posted September 13, 2013 The BBC and maths Professor Marcus du Sautoy explain how changing your mind in an apparently 50/50 gamble can improve your chances of winning. The problem is based on a 1970s American game show, and demonstrates not everything is as it seems. If you thing about it too long then you begin to doubt your own reasoning. Follow the link: http://www.bbc.co.uk/news/magazine-24045598 With the Monty Hall, it isn't a case of 'can', it does. I think what confuses people, is that the host or person opening the doors knows where the prize is. If you don't think of this when trying to work it out, it becomes much harder to comprehend. ---------- Post added 13-09-2013 at 16:33 ---------- It really isn't that hard to understand. You have a 2/3 chance of picking a goat at the start, and if you pick a goat, switching will always get you the car. No, you are wrong. The first door you pick doesn't get opened. Otherwise, you obviously would have a 100% chance of winning if you pick a goat, and the host shows you another goat. ---------- Post added 13-09-2013 at 17:28 ---------- The other one on the page which it asks you to work out, is a good one for prospective drug testing in business. It's quite easy with pen and paper The info given: 1% population have disease. If you have the disease, the test has 99% chance of showing positive (which sounds quite convincing!) If you don't have the disease there is a 2% chance of false result. - Imagine population of 100,000. All are tested. You would get 990 true pos, 97020 true neg, 1980 false pos, 10 false neg. 1000(number of people we know actually have disease)/(990+1980) equals 0.336. Hence a positive result means only 1/3 chance of actually having the disease. Link to comment Share on other sites More sharing options...
Ghozer Posted September 13, 2013 Share Posted September 13, 2013 The BBC and maths Professor Marcus du Sautoy explain how changing your mind in an apparently 50/50 gamble can improve your chances of winning. The problem is based on a 1970s American game show, and demonstrates not everything is as it seems. If you thing about it too long then you begin to doubt your own reasoning. Follow the link: http://www.bbc.co.uk/news/magazine-24045598 I always do that any way... when ever I get a 50/50 choice, I pick one instantly in my head, then consciously change it to the other... and most of the time it makes the difference and i'm right... So many people can't believe it when I do it... The key is, that he's showing the animal first, as the first pick.... if you always pick up their choice first (instead of revealing one that isn't the car) the odds will be even... Link to comment Share on other sites More sharing options...
Gleadly Posted September 13, 2013 Share Posted September 13, 2013 This was explained on Numb3rs the other night. It was 100% clear. (I think). Link to comment Share on other sites More sharing options...
Happ Hazzard Posted September 13, 2013 Share Posted September 13, 2013 No, you are wrong. The first door you pick doesn't get opened. Otherwise, you obviously would have a 100% chance of winning if you pick a goat, and the host shows you another goat. You misunderstand me. You should always switch because it gives you a 2/3 chance of winning as opposed to 33% when you pick at the start. As long as you pick a goat at the beginning (66% chance) you will win if you switch. Only contestants who pick the car at the beginning (33% chance) will lose if they switch. Link to comment Share on other sites More sharing options...
Mikes10 Posted September 13, 2013 Author Share Posted September 13, 2013 Consider the problem if there are lots of doors- say 100 (Total_Doors). There are 100 doors, behind 1 door is the prize, the remainder have goats. So pick a door. You have a 1 in 100 chance of picking the prize. That is; a very good chance of picking a goat:- remember you have probably got a goat. The host knows what's behind every door, The rules say a) if the chosen door contains the prize the host must open 98 doors (Total_Doors - 2 ) containing goats, leaving the chosen door and a goat door b) if the chosen door contains a goat the host must open 98 (Total_Doors - 2 ) doors containing goats, leaving the chosen (goat) door and the prize door You are now given the opportunity to stick or switch ( remember when you started off you have probably picked a goat ). So you switch, and there is a very good chance of winning the prize. The above rules apply for any number of doors, in the Monty Hall example the total number of doors is 3, so the host can only open 1 door. Link to comment Share on other sites More sharing options...
*_ash_* Posted September 13, 2013 Share Posted September 13, 2013 You misunderstand me. You should always switch because it gives you a 2/3 chance of winning as opposed to 33% when you pick at the start. As long as you pick a goat at the beginning (66% chance) you will win if you switch. Only contestants who pick the car at the beginning (33% chance) will lose if they switch. I see what you mean. You first post was a bit short. Link to comment Share on other sites More sharing options...
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