Join TSR now and get all your revision questions answeredSign up now

S2 Help-Binomial and Poisson Watch

    • Thread Starter
    Offline

    0
    ReputationRep:
    Hi guys, can u help me wit this question:
    Flaws in a certain brand of tape occur at random and a rate of 0.75 per 100 m
    Assumin a Poisson is used for the no of flaws in a 400 m roll of tape.
    a) Find the probability of at least one flaw (Done)
    b) Shows that probability that at most ther will be 2 flaws is 0.4232 (Done)

    In a batch of 5 rolls, each of length 400m
    c) Find the probability that 2 rolls will contain less than 5 flaws (Need help )

    thanks
    Offline

    2
    ReputationRep:
    You still need help with this mate??

    These are the type of question that you can easily get stuck on in an exam because you are expecting to use your knowledge of poisson but it isn't the case with (c)

    You can see that the probability of any given roll of tape having less than 5 flaws is .8153

    If your talking about 5 different rolls and you want the probability of two of them containing less than 5 flaws, then there are 10 different ways this can happen (5 C 2 )

    SO this gives us a binomial distribution, X - (5 , .8153)

    You want P(X=2) --> 5C2 x (8153)^2 x (.1847)^3

    this should give you the answer, quote me and let me know
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by MikeySwansea)
    You still need help with this mate??

    These are the type of question that you can easily get stuck on in an exam because you are expecting to use your knowledge of poisson but it isn't the case with (c)

    You can see that the probability of any given roll of tape having less than 5 flaws is .8153

    If your talking about 5 different rolls and you want the probability of two of them containing less than 5 flaws, then there are 10 different ways this can happen (5 C 2 )

    SO this gives us a binomial distribution, X - (5 , .8153)

    You want P(X=2) --> 5C2 x (8153)^2 x (.1847)^3

    this should give you the answer, quote me and let me know
    Thats what i was thinkin for part (c) as well, but yur answer gives a probabilty of 0.04188, but the book says 0.702
    Btw thanks for yur help
    Offline

    2
    ReputationRep:
    That answer seems way too high for me.

    Would love to see what others think as I could easily be wrong.
    • Study Helper
    Offline

    3
    (Original post by MikeySwansea)
    That answer seems way too high for me.

    Would love to see what others think as I could easily be wrong.
    The OP's wording of the question is incorrect, see:

    http://uk.answers.yahoo.com/question...7024807AAqpNk0
    Offline

    2
    ReputationRep:
    Cheers for that Ghostwalker.
    • Thread Starter
    Offline

    0
    ReputationRep:
    Oh thnx for that guys, appreciate it
    • Thread Starter
    Offline

    0
    ReputationRep:
    ooh guys, is ther a quicker way to calculate the binomial or poisson distribution on the calculator if the parameter is not in the table and the formula is too long to use
    • Study Helper
    Offline

    3
    (Original post by sl96)
    ooh guys, is ther a quicker way to calculate the binomial or poisson distribution on the calculator if the parameter is not in the table and the formula is too long to use
    Not that I'm aware of, and I would think it unlikely you'd get anything requiring a great deal of computation at A-level.
 
 
 
Poll
How are you feeling about Results Day?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.