Thread: Expected value Problem

For a game played using the dice in Problem #13, you make a 2$ bet on the outcome of a roll of the dice. If the roll is 5 or lower you win 3$. If the roll is 11 or 12, you win 10$. What is the expected value of this game?(note the winning amounts are net amounts.)

Here is the dice probability distribution for problem 13



Here is what i did



Is this correct?

Originally Posted by solace

For a game played using the dice in Problem #13, you make a 2$ bet on the outcome of a roll of the dice. If the roll is 5 or lower you win 3$. If the roll is 11 or 12, you win 10$. What is the expected value of this game?(note the winning amounts are net amounts.)

Here is the dice probability distribution for problem 13



Here is what i did



Is this correct?

I can't read this last table, but the probability of rolling a 5 or less is 0.3225
and the prob of rolling a 11 or 12 is 0.0175, and the probability of any other
result is 1-0.3225-0.0175 = 0.66.

Now the value of the game is:

0.3225*5 + 0.0175*10 - 0.66*2 = +0.4675

RonL

Originally Posted by CaptainBlack

I can't read this last table, but the probability of rolling a 5 or less is 0.3225
and the prob of rolling a 11 or 12 is 0.0175, and the probability of any other
result is 1-0.3225-0.0175 = 0.66.

Now the value of the game is:

0.3225*5 + 0.0175*10 - 0.66*2 = +0.4675

RonL

Why .3225*5? Should it be *3 since thats how much money you get if you roll a 5 or lower?

Also why .3325?

.09+.09+.1425+.15= .4725 right?

THen 1-.4725+.0175 = .5100

so: .4725*3+.0175*10-.51*2= .5725

Also, doesnt the net value mean that you lose the 2$ you bet and any winnings are -2? So the 3$ win is actually 1$ net profit, and the 10$ win is actually 8$ net profit?

So should i times the probabilities by 1 and 8 instead?

Originally Posted by solace

Why .3225*5? Should it be *3 since thats how much money you get if you roll a 5 or lower?

If that is what you mean net amount. It is an odd way of expressing it but
if you have it defined that way OK.

Also why .3325?

.09+.09+.1425+.15= .4725 right?

THen 1-.4725+.0175 = .5100

so: .4725*3+.0175*10-.51*2= .5725

yes, slip of the calculator

Also, doesnt the net value mean that you lose the 2$ you bet and any winnings are -2? So the 3$ win is actually 1$ net profit, and the 10$ win is actually 8$ net profit?

So should i times the probabilities by 1 and 8 instead?

If that is what you mean by net winnings (I would interpret net winnings
to be how much better off you are after compared to before the bet), then:

0.4725*1 + 0.0175*8 - 0.51*2 = +0.4675

My experience is that when you bet your returned stake is not counted
part of your winnings. Just think of the fun the tax man would have if it did.

RonL

Hello, solace!

You make a $2 bet on the outcome of a roll of the dice.
If the roll is 5 or lower you win $3.
If the roll is 11 or 12, you win $10.
What is the expected value of this game?

Rolling a pair of dice, there are 36 possible outcomes.

The totals and their respective probabilities are:

. .
. .








Hence: .


Therefore, you can expect to win an average of about 30½¢ per game.

Originally Posted by Soroban

Hello, solace!

Rolling a pair of dice, there are 36 possible outcomes.

The totals and their respective probabilities are:

. .
. . \end{array}" alt="
\end{array}" />

\frac{1}{36} + \frac{2}{36} + \frac{3}{36} + \frac{4}{36} \;=\;\frac{10}{36}" alt="
\frac{1}{36} + \frac{2}{36} + \frac{3}{36} + \frac{4}{36} \;=\;\frac{10}{36}" />






Hence: .


Therefore, you can expect to win an average of about 30½¢ per game.

They are not fair dice.

RonL