# probability distribution question

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yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks

Also should i expect all the values in the table to add up to one?

thanks

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#3

(Original post by

yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks

**vix.xvi**)yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks

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(Original post by

The fifth roll is final. The probabilities should add to 1, by definition.

**mqb2766**)The fifth roll is final. The probabilities should add to 1, by definition.

(Original post by

Values in table should add up to 1.

**DFranklin**)Values in table should add up to 1.

so to work out the 5th roll you just do

(3/7)^4 x (4/7) right?

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#5

**vix.xvi**)

yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks

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(Original post by

once you have gone past 4 spins you know that you are on the final spin as the game stops. so to find P ( x = 5 ) you just work out 1 - P ( x < 5 )... in other words add up the previous 4 answers and subtract from 1.

**the bear**)once you have gone past 4 spins you know that you are on the final spin as the game stops. so to find P ( x = 5 ) you just work out 1 - P ( x < 5 )... in other words add up the previous 4 answers and subtract from 1.

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)

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#7

(Original post by

ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)

**vix.xvi**)ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)

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(Original post by

There is no assumption of the colour on the fifth throw.

**mqb2766**)There is no assumption of the colour on the fifth throw.

that makes sense, thank you!!

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#9

**the bear**)

once you have gone past 4 spins you know that you are on the final spin as the game stops. so to find P ( x = 5 ) you just work out 1 - P ( x < 5 )... in other words add up the previous 4 answers and subtract from 1.

**vix.xvi**)

ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)

**But you're going to stop after the 5th roll regardless of whether you roll a G on the 5th roll**. So you just want (3/7)^4.

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#10

(Original post by

In this case it's probably easier to directly work out P(x > 4) (i.e. P(no G's on previous rolls)).

(3/7)^4 x (4/7) is the probability of not rolling a G on the first 4 rolls and then rolling a G on the 5th.

**DFranklin**)In this case it's probably easier to directly work out P(x > 4) (i.e. P(no G's on previous rolls)).

(3/7)^4 x (4/7) is the probability of not rolling a G on the first 4 rolls and then rolling a G on the 5th.

**But you're going to stop after the 5th roll regardless of whether you roll a G on the 5th roll**. So you just want (3/7)^4.
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**DFranklin**)

In this case it's probably easier to directly work out P(x > 4) (i.e. P(no G's on previous rolls)).

(3/7)^4 x (4/7) is the probability of not rolling a G on the first 4 rolls and then rolling a G on the 5th.

**But you're going to stop after the 5th roll regardless of whether you roll a G on the 5th roll**. So you just want (3/7)^4.

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#12

**vix.xvi**)

ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)

^{4}* 1

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#14

(Original post by

wait why is it multiplied by 1?

**vix.xvi**)wait why is it multiplied by 1?

throw. 1 is the probability that once you get to the 5th throw, you finish.

Obviously the "multiply by 1" doesn't actually do anything, but it's in contrast to the previous rounds where there's a 4/7 chance of finishing.

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(Original post by

(3/7)^4 is the probability you get to the 5th

throw. 1 is the probability that once you get to the 5th throw, you finish.

Obviously the "multiply by 1" doesn't actually do anything, but it's in contrast to the previous rounds where there's a 4/7 chance of finishing.

**DFranklin**)(3/7)^4 is the probability you get to the 5th

throw. 1 is the probability that once you get to the 5th throw, you finish.

Obviously the "multiply by 1" doesn't actually do anything, but it's in contrast to the previous rounds where there's a 4/7 chance of finishing.

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