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Further probability question

  • 22-03-2010 03:56PM
    #1
    eoins23456
    Registered Users, Registered Users 2 Posts: 603 ✭✭✭


    Bit confused with this question that was on the further probability question on examcraft mock.It says 95percent level of significance but usually it says 5 percent.gave the question a go anyway but kinda confused as to why they said 95.not sure if my solution is correct or way off.any help is much appreciated


    The mean number of sweet contained in packets of sweets is stated by the manufacturer to be 96,with a standard deviation of 5.A sample of 100 packets was selected at random and found to have a mean packet content of 93 sweets. At the 95 percent level of significance,is there evidence to suggest that the mean number of sweets is less then 96?

    My solution:
    i said this is a one tailed test as its in a definite direction ie less then 96
    93-96/5/square root of1oo=-3/.5=-6 which is less the -1.645
    therefore reject null hypothesis.evidence there to suggest number of sweets is less then 96

    Is this right or wrong?


Comments

  • #2
    MathsManiac
    Registered Users, Registered Users 2 Posts: 1,595 ✭✭✭MathsManiac


    You're correct. The use of 95% instead of 5% was almost certainly an error on the part of the question writer. (A 5% level of significance in a two-tailed hypothesis test corresponds closely to a 95% confidence interval, and this may have led to the error - a slip of the pen, so to speak!)

    Your solution is a correct test of the hypothesis at the 5% level of significance.


  • #3
    eoins23456
    Registered Users, Registered Users 2 Posts: 603 ✭✭✭eoins23456


    thanks very much:D.am i correct in saying its a one tailed test?


  • #4
    MathsManiac
    Registered Users, Registered Users 2 Posts: 1,595 ✭✭✭MathsManiac


    Yes, for the reason you stated.


  • #5
    eoins23456
    Registered Users, Registered Users 2 Posts: 603 ✭✭✭eoins23456


    any chance anyone has any sample questions for further probability and statistics?ive done all the ones in texts and tests and the exam papers.


  • #6
    MathsManiac
    Registered Users, Registered Users 2 Posts: 1,595 ✭✭✭MathsManiac


    eoins23456 wrote: »
    any chance anyone has any sample questions for further probability and statistics?ive done all the ones in texts and tests and the exam papers.

    You could always try to get hold of the supplementary booklets that the authors of the other text books produced: Oliver Murphy (Folens) and Aidan Roantree (School & College publishing or CJ Fallon???)


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  • #7
    eoins23456
    Registered Users, Registered Users 2 Posts: 603 ✭✭✭eoins23456


    I Recently heard it was out of print but managed to email Oliver Murphy who very kindly said he would photocopy his copy for me.Thanks for the idea


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