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Math Help - Need help finding mu

  1. #1
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    Need help finding mu

    Ok I have to do a 2 sample t-test so i have 2 different sets of data that are similar to this.
    boy grades = 90,87,77,97,64,76,88,93,83,79
    girl grades = 100,95,69,77,85,89,78,90,66,81
    alpha = .05

    If i take the average of each set, I can find the x-bar but i need to find the mu in order to complete the test statistic. Any help is appreciated, thanks
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  2. #2
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    You you need to establish if there is any difference between the two sets then the null hypothesis is

    \displaystyle H_0 : \mu_1 - \mu_2 = 0

    and

    \displaystyle H_A : \mu_1 - \mu_2 \neq 0

    The \displaystyle \mu_0 you require is the hypothesised difference so make \displaystyle \mu_0=0 in your test statistic.
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  3. #3
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    The formula includes mu0 and mu1 though, so what would i put in that place?
    Also, wouldn't the null hypothesis be mu0-mu1= c, where c = some constant
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  4. #4
    MHF Contributor matheagle's Avatar
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    I thought Moo was online.
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  5. #5
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    Quote Originally Posted by matheagle View Post
    I thought Moo was online.
    Am I missing something? Sorry if I don't get the reference. o.0
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  6. #6
    MHF Contributor matheagle's Avatar
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    was a joke about Moo=mu
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  7. #7
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    Quote Originally Posted by matheagle View Post
    was a joke about Moo=mu
    Oh okay. Although, that doesn't really help xD. I just want to confirm: the mu0 and mu1 in the formula are both set equal to 0? Also, if the sample sizes are the same, the degrees of freedom is n1 + n2 - 2, right? Thanks for the help
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  8. #8
    MHF Contributor matheagle's Avatar
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    well someone needs to win some joke points away from Mr Fantasy
    OK, back to YOUR question.
    We need more information.
    First of all, what are you trying to prove?
    we need to know, what the alternative hypoethesis is.
    Next we need to knw if this is a paired difference experiment, since we
    have the same number of boys and girls.
    But I doubt that it is a paired diff experiment.
    Next we need to know if the population variances are equal or not.
    They seem to be, if thats the case.
    The test stat would be

    {(\bar X_1-\bar X_2)-(\mu_1-\mu_2)\over s_p\sqrt{{1\over n_1}+{1\over n_2}}

    where we are pooling the sample variances.
    Then we need to know if this is a one-sided or two-sided test.
    So, you need to tell me what they are asking you to prove
    and the distribution under the null hypothesis would be a t with df
    equal to the sum of the two sample sizes minus two.
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