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Statistics Question Urgent Help

Doing an S2 question and I don't get this
Biased 4 sided spinner can only land on 1,2,3,4
Random Variable X is the number that the spinner lands on after a single spin
P(X=q) = P(X=q+2) for q=1.2
Given P(X=2) = 0.35


(a) Find the complete probability distribution of q


(b) spinner spinned 50 times
find probability more than half land on number 4

The random variable
12
Y= ----
X
Find P (Y-X<=4)
Find P( Y - X less or equal to 4)
(edited 5 years ago)

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Reply 1
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Reply 2
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Reply 3
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Original post by Pakora99
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Insufficient information to resolve the problem - unless it's to be left in terms of a parameter.

Please link the original question.
Reply 5
Original post by ghostwalker
Insufficient information to resolve the problem - unless it's to be left in terms of a parameter.

Please link the original question.


sorry bout that forgot to add this bit Given P(X=2) = 0.35
updated it at the top as well
Original post by Pakora99
sorry bout that forgot to add this bit Given P(X=2) = 0.35
updated it at the top as well


From the question, then:

P(X=2) = P(X=4) = 0.35

P(X=1) = P(X=3) = ?

And use the fact that the total probability must be 1, to work out the unknown value.
Reply 7
Original post by ghostwalker
From the question, then:

P(X=2) = P(X=4) = 0.35

P(X=1) = P(X=3) = ?

And use the fact that the total probability must be 1, to work out the unknown value.


P(X=2) = P(X=4) = 0.35 how do you know 2 and 4 are related
Reply 8
Original post by ghostwalker
From the question, then:

P(X=2) = P(X=4) = 0.35

P(X=1) = P(X=3) = ?

And use the fact that the total probability must be 1, to work out the unknown value.

so P(X=1) = 0.15
P(X=3) =0.15
Original post by Pakora99
P(X=2) = P(X=4) = 0.35 how do you know 2 and 4 are related


Question tells you.

"P(X=q) = P(X=q+2) for q=1.2"

Setting q=2

P(X=2) = P(X=4)
Reply 10
Original post by ghostwalker
Question tells you.

"P(X=q) = P(X=q+2) for q=1.2"

Setting q=2

P(X=2) = P(X=4)


Ahh Thank You!!!
Original post by Pakora99
so P(X=1) = 0.15
P(X=3) =0.15


Yes.

Can you do part b? If not, what distribution do you thnk it is?
Reply 12
Original post by ghostwalker
Yes.

Can you do part b? If not, what distribution do you thnk it is?


Looks like binomial distribution so I've done
1-P(X<25) = P(X>25)
1-P(X{less or equal} 25) = P(X>25)
let x be 0.35
0.989956 for P(X<25)
1-0.989956=0.01
not too sure on this bit if I've done It right
Original post by Pakora99
Looks like binomial distribution so I've done
1-P(X<25) = P(X>25)
1-P(X{less or equal} 25) = P(X>25)


Yes, should be \leq


let x be 0.35


p=0.35
Probability of success on a single spin.


0.989956 for P(X<25)
1-0.989956=0.01
not too sure on this bit if I've done It right


Yep.
Reply 14
Original post by ghostwalker
Yes, should be \leq



p=0.35
Probability of success on a single spin.



Yep.


y=12/X
FindP(Y−X≤4)
I was thinking about finding in the 50 spins where X is less or equal to 4
But how would I do the Y bit?
Sorry about no latex I can't figure out how to use it
(edited 5 years ago)
Original post by Pakora99
y=12/X
FindP(Y−X≤4)
I was thinking about finding in the 50 spins where X is less or equal to 4
But how would I do the Y bit?
Sorry about no latex I can't figure out how to use it


The 50 spins don't come into it, unless there's something you've not posted.

You're only dealing with 1 spin, with r.v. X

So, you just need to check when (12/X)X4(12/X)- X \leq 4. There are only 4 values, with their corresponding probabilities.
Reply 16
Original post by ghostwalker
The 50 spins don't come into it, unless there's something you've not posted.

You're only dealing with 1 spin, with r.v. X

So, you just need to check when (12/X)X4(12/X)- X \leq 4. There are only 4 values, with their corresponding probabilities.


If P(X<=4) then
all values less than it is 0.65 and including is equal to 1
cuz P(X=4) is 0.35 all values less is 0.65
(edited 5 years ago)
Original post by Pakora99
If P(X<=4) then
all values less than it is 0.65 and including is equal to 1
cuz P(X=4) is 0.35 all values less is 0.65


OK, I think I know what you mean, but so what!

You're interested in P(12/X-X<= 4), not P(X<= 4)

You need to evaluate that function over the domain of X, i.e. 1,2,3,4. And check if that function is <=4.
(edited 5 years ago)
Reply 18
Original post by ghostwalker
OK, I think I know what you mean, but so what!

You're interested in P(12/X-X<= 4), not P(X<= 4)

You need to evaluate that function over the domain of X, i.e. 1,2,3,4. And check if that function is <=4.


I don't know where to start
Original post by Pakora99
I don't know where to start


IF X=1, then (12/X)-X = (12/1)-1 = 11.

This is >4, so we don't include P(X=1) in the sum of the probability.

Etc.

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