What's new
USCHO Fan Forum

This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

  • The USCHO Fan Forum has migrated to a new plaform, xenForo. Most of the function of the forum should work in familiar ways. Please note that you can switch between light and dark modes by clicking on the gear icon in the upper right of the main menu bar. We are hoping that this new platform will prove to be faster and more reliable. Please feel free to explore its features.

Monty Hall, we have a PROBLEM

Re: Monty Hall, we have a PROBLEM

Albert and Bernard just met Cheryl. “When’s your birthday?” Albert asked Cheryl.

Cheryl thought a second and said, “I’m not going to tell you, but I’ll give you some clues.” She wrote down a list of 10 dates:

May 15 — May 16 — May 19

June 17 — June 18

July 14 — July 16

August 14 — August 15 — August 17

“My birthday is one of these,” she said.

Then Cheryl whispered in Albert’s ear the month — and only the month — of her birthday. To Bernard, she whispered the day, and only the day.

“Can you figure it out now?” she asked Albert.

Albert: I don’t know when your birthday is, but I know Bernard doesn’t know, either.

Bernard: I didn’t know originally, but now I do.

Albert: Well, now I know, too!

When is Cheryl’s birthday?
 
Re: Monty Hall, we have a PROBLEM

Albert and Bernard just met Cheryl. “When’s your birthday?” Albert asked Cheryl.

Cheryl thought a second and said, “I’m not going to tell you, but I’ll give you some clues.” She wrote down a list of 10 dates:

May 15 — May 16 — May 19

June 17 — June 18

July 14 — July 16

August 14 — August 15 — August 17

“My birthday is one of these,” she said.

Then Cheryl whispered in Albert’s ear the month — and only the month — of her birthday. To Bernard, she whispered the day, and only the day.

“Can you figure it out now?” she asked Albert.

Albert: I don’t know when your birthday is, but I know Bernard doesn’t know, either.

Bernard: I didn’t know originally, but now I do.

Albert: Well, now I know, too!

When is Cheryl’s birthday?

Why can't she just show us the long form birth certificate already? I'm just asking questions!
 
Re: Monty Hall, we have a PROBLEM

The Albert, Bernard and Cheryl's Birthday problem looks to me a like a pretty good discrete math problem, if you arrange the dates just right. But in plain English here's how I approached it:

... Cheryl then tells Albert and Bernard separately the month and the day of her birthday, respectively.

Albert: I don't know when Cheryl's birthday is, but I know that Bernard does not know too.
She gave Albert one of the months that does not have a unique date (July or August).
May and June are out.

Bernard: At first I didn't know when Cheryl's birthday is, but I know now.
14 is out, because Bernard can't guess July or August in order to make that statement. She gave Bernard 15, 16 or 17.
Albert: Then I also know when Cheryl's birthday is.
August is out, because Albert can't guess 15 or 17 to make that statement.
So 15 and 17 are out.


All that's left is July 16.
 
Re: Monty Hall, we have a PROBLEM

OK, so it's PowerBall fever!

Let's say that I buy one ticket with two entries on it, then stick it in a drawer without looking at the numbers at all.

Sunday morning, I wake up and hear on the news that somebody won the $800 million jackpot (let's say it is discounted to $545 million on a present value basis, and let's assume a 45% income tax rate overall, so that the net after-tax value is $300 million).

1) What is the minimum price I accept to sell my ticket to someone else, assuming I still haven't looked at any of the actual numbers?

2) Later that day, I hear on the news that the winning ticket was sold in my state, too. Now what is the minimum price I accept to sell my ticket, if I still haven't looked at it yet?

3) Then I hear the next morning that someone in my town was the winner. Same question, same constraint.

(answer may not be in actual dollars, it might be in P[SUB]S[/SUB] (Tickets sold in my state as ratio to all tickets sold) or P[SUB]T[/SUB] (ratio for tickets sold in town compared to all sold). Note that my one ticket has two numbers on it.
 
Re: Monty Hall, we have a PROBLEM

OK, so it's PowerBall fever!

Let's say that I buy one ticket with two entries on it, then stick it in a drawer without looking at the numbers at all.

Sunday morning, I wake up and hear on the news that somebody won the $800 million jackpot (let's say it is discounted to $545 million on a present value basis, and let's assume a 45% income tax rate overall, so that the net after-tax value is $300 million).

1) What is the minimum price I accept to sell my ticket to someone else, assuming I still haven't looked at any of the actual numbers?

2) Later that day, I hear on the news that the winning ticket was sold in my state, too. Now what is the minimum price I accept to sell my ticket, if I still haven't looked at it yet?

3) Then I hear the next morning that someone in my town was the winner. Same question, same constraint.

(answer may not be in actual dollars, it might be in P[SUB]S[/SUB] (Tickets sold in my state as ratio to all tickets sold) or P[SUB]T[/SUB] (ratio for tickets sold in town compared to all sold). Note that my one ticket has two numbers on it.

Better start with the assumption that you found a gopher fan who will give you money believing you have not looked at the numbers.
 
Re: Monty Hall, we have a PROBLEM

Not enough info to solve. How many tickets were sold in your state? How many were sold in your city? Did you purchase your tickets within your city?
 
Re: Monty Hall, we have a PROBLEM

Better start with the assumption that you found a gopher fan who will give you money believing you have not looked at the numbers.


Lol. You're confusing us with the paint thinner drinkers to the east.
 
Re: Monty Hall, we have a PROBLEM

Not enough info to solve. How many tickets were sold in your state? How many were sold in your city? Did you purchase your tickets within your city?

Use scalar (Ts, Tc, whatever). Assume I bought in my town. or don't bother trying at all. whichever.

One of the tricky parts in the problem is estimating the odds of multiple winners....
 
Re: Monty Hall, we have a PROBLEM

Use scalar (Ts, Tc, whatever). Assume I bought in my town. or don't bother trying at all. whichever.

One of the tricky parts in the problem is estimating the odds of multiple winners....

And for those of us who ended their mathematics studies with applied calculus, how are we supposed to know to use scalar or what that even means now that we know it?
 
Re: Monty Hall, we have a PROBLEM

And for those of us who ended their mathematics studies with applied calculus, how are we supposed to know to use scalar or what that even means now that we know it?

sorry, I merely meant use a symbol to represent a number whose magnitude is unknown to you.

like c is the speed of light in a vacuum....nothing more than that. T is total tickets sold, Ts tickets in my state, Tt tickets in my town, whatever.

As I alluded, the vexation in the problem is "what are odds of splitting the prize" not so much, "once prize has been won (at least once), what are odds of holding winning ticket" though both are a bit gnarly.

Some of the math is reminiscent of our thread title: you get to pick one of three doors, they open a door that doesn't have the prize, so then do you switch your original choice, or keep it?

The odds before the drawing are x, but after the drawing is over and (at least) one winner is certain, how do the odds change?

This problem actually is probably too hard to solve as I posted it, because one also has to factor in winning something other than the jackpot as well.





at least I am not -100%....
 
Last edited:
Re: Monty Hall, we have a PROBLEM

Way too many unknowns - not just how many tickets sold, but how many unique guesses? And, if there was definitely a winner, how many people have already looked at a ticket with a unique losing combo? Every time that happens, your odds of winning go up.

Thought experiment extreme: 100M tickets sold, but all the other tickets guessed the same combo. As soon as a single other person checks his ticket and loses, your probability of winning becomes 100%. If the 100M were divided among 2 guesses (that are both different from yours), then when one loser checks his ticket, your probability is 50% - it's either your ticket or the 50M people who guessed the 3rd combo. Etc.
 
Re: Monty Hall, we have a PROBLEM

So like most offices we have a Super Bowl box pool. $20 for five squares (or $5 for one square). We have enough people to fill two boxes.

I am going to partner with someone to put in $40 total between us. Are we better off both in the same box, or in different boxes?

My intuition says that we are "probably" better off with both of us being in the same box, as that gives us 10 chances to win something in that particular box instead of five. (10% chance to win something in one box, 0% chance in other; compared to 5% chance to win in each box).

However, I'm not convinced that the edge is as great as it first appears to be, since it also reduces the chances we could be big winners in both boxes.

Payout is 10% for 1st quarter, 20% for halftime, 10% for 3rd quarter, 60% for final score (nothing for 4th quarter if there is OT). If we assume $400 for each box (everyone puts in $20).

If scores and distribution of boxes is random, hmm....

10% of 400 + 0% of 400 = 5% of 200 + 5% of 200 so I am having trouble reconciling my intuition with math here, I think the math is missing something though since we might have duplication of numbers if spread over 2 boxes...but on a net basis, is duplication bad? (both lose) or good? (both win).

Maybe both of us in one box has better chance of winning something while each of us in separate box has less likely chance but bigger potential payout (shorter wider distribution vs taller narrower distribution with same area under each).

Some days I wish I had gone beyond statistics 101....





PS I always thought it would be fun to have a secondary market after the random selection of boxes. Would getting some combination of 7, 3, 0 be worth more than others?
 
Last edited:
So like most offices we have a Super Bowl box pool. $20 for five squares (or $5 for one square). We have enough people to fill two boxes.

I am going to partner with someone to put in $40 total between us. Are we better off both in the same box, or in different boxes?

My intuition says that we are "probably" better off with both of us being in the same box, as that gives us 10 chances to win something in that particular box instead of five. (10% chance to win something in one box, 0% chance in other; compared to 5% chance to win in each box).

However, I'm not convinced that the edge is as great as it first appears to be, since it also reduces the chances we could be big winners in both boxes.

Payout is 10% for 1st quarter, 20% for halftime, 10% for 3rd quarter, 60% for final score (nothing for 4th quarter if there is OT). If we assume $400 for each box (everyone puts in $20).

If scores and distribution of boxes is random, hmm....

10% of 400 + 0% of 400 = 5% of 200 + 5% of 200 so I am having trouble reconciling my intuition with math here, I think the math is missing something though since we might have duplication of numbers if spread over 2 boxes...but on a net basis, is duplication bad? (both lose) or good? (both win).

Maybe both of us in one box has better chance of winning something while each of us in separate box has less likely chance but bigger potential payout (shorter wider distribution vs taller narrower distribution with same area under each).

Some days I wish I had gone beyond statistics 101....





PS I always thought it would be fun to have a secondary market after the random selection of boxes. Would getting some combination of 7, 3, 0 be worth more than others?

While I don't understand the specifics of your superb owl pool, it sounds like a variation of the "draw a number, and if it matches [total points, score differential, some condition X], you win" and there are enough participants to have two separate pools, of which you can contribute to one or both.

Your overall odds of winning, assuming all possibilities are equally likely to win, is simply the number of possibilities in your control divided by the total number of possibilities, regardless of how they're broken down.

At its simplest, think of flipping two coins, so there are four potential bets you could make (H1, T1, H2, T2). It costs you $1 to cover one of those. You decide to partner up with someone else to cover two possibilities. You could each take a different side of the same coin, guaranteeing you'll break even, but only break even. One of your bets must lose while the other must win, and you can't win anything from the other coin since you have no money on it.

If instead you each take one side on each coin, you will still be expected to break even. 1/2 the time that will actually happen, 1/4 of the time you'll lose both dollars, and 1/4 of the time you'll come out $2 ahead.

Or another way to think of it is like keno. Your choice is essentially like choosing between playing multiple tickets for a single drawing, or one ticket for multiple drawings. All else being equal, your overall expected value doesn't change.
 
Last edited:
Back
Top