Results 1 to 12 of 12

Math Help - Hypotheses testing - apparently crying isn't going to help

  1. #1
    Newbie
    Joined
    May 2012
    From
    UK
    Posts
    15

    Hypotheses testing - apparently crying isn't going to help

    So that is the entire day wasted.

    I have no idea what I am supposed to be doing here, an assignment due in next week and only in the second question (which is the above). I distance learn so can't just pop and see a teacher.

    I am just reading this and don't even understand half of the words and can't find anything similar anywhere.

    Basically, I have two sets of information - comparing the effects of alcohol on two similar illnesses - I am given the sample number for the first, and the number of drinkers- and the same for the second illness.

    I have to create distribution models for both - I created Binomial distribution for both of them.
    Then I need to write the null and alternative hypotheses used to test the proportion differences/similarities.

    I am sorry to be so emotional haha - but if I can't do this, I have no hope with the rest of the assignment and I don't know what to do :-(
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member ILikeSerena's Avatar
    Joined
    Dec 2011
    Posts
    733
    Thanks
    121

    Re: Hypotheses testing - apparently crying isn't going to help

    Quote Originally Posted by SamanthaJane View Post
    So that is the entire day wasted.

    I have no idea what I am supposed to be doing here, an assignment due in next week and only in the second question (which is the above). I distance learn so can't just pop and see a teacher.

    I am just reading this and don't even understand half of the words and can't find anything similar anywhere.

    Basically, I have two sets of information - comparing the effects of alcohol on two similar illnesses - I am given the sample number for the first, and the number of drinkers- and the same for the second illness.

    I have to create distribution models for both - I created Binomial distribution for both of them.
    Then I need to write the null and alternative hypotheses used to test the proportion differences/similarities.

    I am sorry to be so emotional haha - but if I can't do this, I have no hope with the rest of the assignment and I don't know what to do :-(
    Hi SamanthaJane!

    It sounds a bit like you're supposed to do a 2-way ANOVA test.
    But it depends a bit on the actual data you have.

    Can you tell us a bit more about your data?
    What is it that was actually measured?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2012
    From
    UK
    Posts
    15

    Re: Hypotheses testing - apparently crying isn't going to help

    Thanks for replying IlikeSerena,

    I have managed to calm myself down a bit - temporarily!
    I can't really say anymore because it is a marked assignment. But I look into ANOVA testing - it is only 2 points, but the rest is on minitab so will have to try figure that out!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member ILikeSerena's Avatar
    Joined
    Dec 2011
    Posts
    733
    Thanks
    121

    Re: Hypotheses testing - apparently crying isn't going to help

    Sure!
    Let us know if you have any questions.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    May 2012
    From
    UK
    Posts
    15

    Re: Hypotheses testing - apparently crying isn't going to help

    Actually, I do have one :-)
    I thought I was doing really well with this - took a few days - but seem to have got there.

    What I missed in the question was, although n=10 they told us to 'assume normal distribution'

    So back to square one!

    I have used xbar-mu / s/sqrtn to get the test stat - I also need the null distribution which I think is;N(mu,sigma^2) - So I have used mu from my null hypothesis and s^2 for the pop variation - is that correct?

    But now I am trying to get the rejection zone - and I keep getting +/-1.96 as it is a 5% confidence interval, but when I use minitab I get totally different answers, and have no idea where they came from.

    Any clues? I am fairly sure I am making errors all the way through!
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member ILikeSerena's Avatar
    Joined
    Dec 2011
    Posts
    733
    Thanks
    121

    Re: Hypotheses testing - apparently crying isn't going to help

    When you have n=10 and no information on sigma, you are supposed to do a t-test instead of a z-test.
    Your formula is correct, but you need to look it up in a t-table with n-1=9 degrees of freedom.
    This is what minitab will have done.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    May 2012
    From
    UK
    Posts
    15

    Re: Hypotheses testing - apparently crying isn't going to help

    oh!!! That is great, so I can perhaps salvage some of my earlier work?
    Even though the question states specifically that it can be modelled by a normal distribution?
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Super Member ILikeSerena's Avatar
    Joined
    Dec 2011
    Posts
    733
    Thanks
    121

    Re: Hypotheses testing - apparently crying isn't going to help

    The t-test also assumes a normal distribution - it's just with an unknown sigma that is approximated by the standard deviation of the sample.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Newbie
    Joined
    May 2012
    From
    UK
    Posts
    15

    Re: Hypotheses testing - apparently crying isn't going to help

    Oh - I thought it was two totally seperate tests - one for below 30 samples and one for above 30 samples.

    So actually, my original answer should be correct - although in that I showed a T distribution - T~T(n-1) rather than an N one - N(mu, sigma^2)- which one is correct?
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Newbie
    Joined
    May 2012
    From
    UK
    Posts
    15

    Re: Hypotheses testing - apparently crying isn't going to help

    (as a null distribution?)
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Super Member ILikeSerena's Avatar
    Joined
    Dec 2011
    Posts
    733
    Thanks
    121

    Re: Hypotheses testing - apparently crying isn't going to help

    When n is large enough the corresponding t-distribution is equal to the normal distribution.
    You can see this if you check the t-table.
    Btw, n=30 is still a bit low to switch to a z-test.

    In your case, the assumed null distribution would be the t(n-1) distribution.
    Last edited by ILikeSerena; April 4th 2013 at 09:53 AM.
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Super Member ILikeSerena's Avatar
    Joined
    Dec 2011
    Posts
    733
    Thanks
    121

    Re: Hypotheses testing - apparently crying isn't going to help

    Btw, if n > 30, you can assume that sample mean of any distribution behaves like a normal distribution (central limit theorem).
    To do a t-test, the assumption is that the sample mean is normally distributed.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Hypotheses testing
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: March 5th 2013, 07:21 PM
  2. Hypotheses Testing
    Posted in the Statistics Forum
    Replies: 3
    Last Post: January 10th 2012, 02:39 PM
  3. hypotheses testing
    Posted in the Statistics Forum
    Replies: 2
    Last Post: October 25th 2010, 02:16 PM
  4. hypotheses testing
    Posted in the Advanced Statistics Forum
    Replies: 10
    Last Post: April 5th 2009, 01:38 PM
  5. hypotheses testing
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: March 3rd 2009, 03:24 AM

Search Tags


/mathhelpforum @mathhelpforum