Reply to: Marrying your sister.

[BrilloPad]

Also (snigger), suppose a game show host tells you there's a gold bar behind one of three closed doors and asks you to choose a door (without opening it). The host then opens one of the other doors, revealing no gold bar behind it, and offers to let you change your choice to the third door. Should you switch?

Easier to imagine 1000000 closed doors and 999998 doors are revealed with no gold bar being revealed.

[OwlHoot]

Probability is interesting because it's so counter-intuitive.

Yup, for example it's possible to have three non-transitive dice such that if player 1 picks any one then player 2 can pick one of the others and has a greater probability of winning.

Also (snigger), suppose a game show host tells you there's a gold bar behind one of three closed doors and asks you to choose a door (without opening it). The host then opens one of the other doors, revealing no gold bar behind it, and offers to let you change your choice to the third door. Should you switch?

[EqualOpportunities]

No matter how you write it, it's still spellt i. n. c. e. s. t.

Yes, but it is the game the whole family can play... A bit like The Wheel of Fortune.

[sasguru]

Not in the same year. (unless it's people in a womb, not people in a room).

chances of 2 people having same birthday: 1/365
Number of combinations of 2 people in a set of 23 people: 22+21+20...+3+2+1 = 253.
So chance of at least one of those combinations having same birthday = 253/365 = 69%

Nice attempt but your maths is wrong. As an exercise you can find out why.
Probability is interesting because it's so counter-intuitive.

[thunderlizard]

Not in the same year. (unless it's people in a womb, not people in a room).

chances of 2 people having same birthday: 1/365
Number of combinations of 2 people in a set of 23 people: 22+21+20...+3+2+1 = 253.
So chance of at least one of those combinations having same birthday = 253/365 = 69%

[xoggoth]

an infinite amount of tosses

Getting there.

[sasguru]

and now I'm off to watch that travesty of history, U571

[sasguru]

it is true. google it.

No he's right...not in the same year.
And as for your last post Mr. Ruprecht, there's nothing wrong with Madam Palm and her five lovely daughters I'll have you know ...

[BrilloPad]

in the same year? b0ll0x.

it is true. google it.

[Ruprect]

I think you're thinking about the "random walk". But the law of large numbers means that it will veer back to 0.5 eventually, theoretically after an infinite amount of tosses.

Appropriate for you SAS to be talking about an infinite amount of tosses.

No offence like, but you teed it up.

[Ruprect]

Actually no. If you take just 23 people, the odds of two of them having the same birthday is about 0.5. Strange but true.

in the same year? b0ll0x.

[thunderlizard]

if you toss a coin enough times and the results veer away from 0.5, then tossing the coin more times won't bring the results back to 0.5. I honestly can't remember the details of that one, but that lecturer set his HP programmable calculator on the job for the length of the lecture to prove that point.

Can anyone else here remember similar?

well that just feels like common sense to me. In order to "correct" the results of its previous tossings, the coin would have to "remember" what they were, which, being a simple creature, it won't.

[sasguru]

What degree did you do? General maths?

At Exeter, you could pick units from pure/applied/stats in final year. I did 5 applied and 1 stats. pure always seemed so pointless e.g. principa mathmatica takes 365 pages to prove that 1+1=2.

No. I did a Computer Science degree, much to my regret nowadays. And then a bulltulip Business masters

[BrilloPad]

Is that the hefty tome I saw in the bookshop? It scares me.
I read "The Emperors New Mind" and that was difficult enough. I wish I had done a pure maths degree now.

What degree did you do? General maths?

At Exeter, you could pick units from pure/applied/stats in final year. I did 5 applied and 1 stats. pure always seemed so pointless e.g. principa mathmatica takes 365 pages to prove that 1+1=2.

[BrilloPad]

Indeed I find the maths fascinating. Brillo, I think you would enjoy

"Understanding Probability - Chance Rules in Everyday Life" by Henk Tijms.

appreciate the tip. I like you and like our posts, so I just bought off Amazon. I nearly bauked at £14.50 - I am only a contractor you know!

I guess now you will recommend "great squirrels have known"? :-)