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# S1 Discrete Random Variables Question URGENT HELP!! watch

1. please help (( I know how to calculate the expected mean but I don't know how to work out the probability distribution for both which I need.

I have to leave the house in like 40 minutes and this is due in my first lesson (((

What I get for leaving homework until last minute
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2. (Original post by bluemadhatter)
please help (( I know how to calculate the expected mean but I don't know how to work out the probability distribution for both which I need.

I have to leave the house in like 40 minutes and this is due in my first lesson (((

What I get for leaving homework until last minute
Well, you know that dices can give scores of 1, 2, 3, 4, 5 or 6.

So if you throw two dices, the product of their two scores could be anywhere from 1*1, 1*2, 2*5, 6*6, etc... so you'll need to list each one of those down and calculate the probability of it.

1*1 is the score of 1 on the first die and a score of 1 on the second die, so that's a probability of 1/6 * 1/6 = 1/36
3. (Original post by Zacken)
Well, you know that dices can give scores of 1, 2, 3, 4, 5 or 6.

So if you throw two dices, the product of their two scores could be anywhere from 1*1, 1*2, 2*5, 6*6, etc... so you'll need to list each one of those down and calculate the probability of it.

1*1 is the score of 1 on the first die and a score of 1 on the second die, so that's a probability of 1/6 * 1/6 = 1/36
I don't understand

For 8a) Its asking the probability distribution of Y, the score on a player's turn
and its included all the heads and tails bit as well

and for 9a) It asks for the probability distribution of X (the product of the scores on the top faces)

hmm so is the probability of each score not 1/6 so the probability of each product is 1/6*1/6 = 1/36 does that mean its a uniform distribution?? hmm maybe I DID get this one???
4. (Original post by bluemadhatter)
I don't understand

For 8a) Its asking the probability distribution of Y, the score on a player's turn
and its included all the heads and tails bit as well

and for 9a) It asks for the probability distribution of X (the product of the scores on the top faces)

hmm so is the probability of each score not 1/6 so the probability of each product is 1/6*1/6 = 1/36 does that mean its a uniform distribution?? hmm maybe I DID get this one???
Oh, sorry. I was answering only question 9. It is indeed a uniform distribution for that one. Each product has a probability of 1/36.
5. (Original post by Zacken)
Oh, sorry. I was answering only question 9. It is indeed a uniform distribution for that one. Each product has a probability of 1/36.
Okay thank you, question 9 done Could you help me with 8a please??
6. (Original post by bluemadhatter)
Okay thank you, question 9 done Could you help me with 8a please??
Okay, so we know that the possibilites are 1, 2, ..., 6 just like in the table drawn for you. It'll be the same table, just with different probabilities for each X.

So, for example getting a 1: The probability of this is given by getting a heads, rolling one die and getting a 1 (1/2 * 1/6) added to the probability of getting a tails, rolling two dices and getting a (as the highest score) 1. (1/2 * 1/36) where the 1/36 comes from the table.

Getting a 2: The probability of this is given by getting a heads, rolling one die and getting a 2 (1/2 * 1/6) added to the probability of getting a tails, rolling two dices and the highest score being a 2 (1/2 * 3/36)

Getting a 3: etc...
7. (Original post by Zacken)
Okay, so we know that the possibilites are 1, 2, ..., 6 just like in the table drawn for you. It'll be the same table, just with different probabilities for each X.

So, for example getting a 1: The probability of this is given by getting a heads, rolling one die and getting a 1 (1/2 * 1/6) added to the probability of getting a tails, rolling two dices and getting a (as the highest score) 1. (1/2 * 1/36) where the 1/36 comes from the table.

Getting a 2: The probability of this is given by getting a heads, rolling one die and getting a 2 (1/2 * 1/6) added to the probability of getting a tails, rolling two dices and the highest score being a 2 (1/2 * 3/36)

Getting a 3: etc...
where did this value come from? Is it not 2/36 or 1/36. How did you work out the probability of getting the highest score as 2?

Sorry >.<
8. (Original post by bluemadhatter)
where did this value come from? Is it not 2/36 or 1/36. How did you work out the probability of getting the highest score as 2?

Sorry >.<
In the table given to you, it says "when two fair dice are shown the probability of the highest score being X is shown below". You want P(highest score is 2) in that case, which si the number number 2 in your table.
9. (Original post by Zacken)
In the table given to you, it says "when two fair dice are shown the probability of the highest score being X is shown below". You want P(highest score is 2) in that case, which si the number number 2 in your table.
OOHHHHHHHH OKAY I get it now!!! Thank you so much
10. (Original post by bluemadhatter)
OOHHHHHHHH OKAY I get it now!!! Thank you so much
Glad you got it! Buuut, I think what I said about Q9 is wrong. Groggy mornings and all.

It can't be uniform because some of the numbers can't be reached, i.e: no product will be "7", so they probably want you to find all the possible products and find each probability individually. Sorry.
11. (Original post by Zacken)
Glad you got it! Buuut, I think what I said about Q9 is wrong. Groggy mornings and all.

It can't be uniform because some of the numbers can't be reached, i.e: no product will be "7", so they probably want you to find all the possible products and find each probability individually. Sorry.
Its fine at least I've "attempted" it Now I must run out the house O.O

Thanks again
12. (Original post by bluemadhatter)
Its fine at least I've "attempted" it Now I must run out the house O.O

Thanks again
Glad I "helped".

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