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Math Help - Hypothesis Test

  1. #1
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    Hypothesis Test

    I ve had and am having the hardest time trying to figure out which hypothesis test to use for the following:

    A 2 tailed test
    Known: n = # of trials
    mean for sample 1
    mean for sample 2

    n's are <30 AND population variances are NOT known. Since variances are not known, I should use a t-test, but then in order to get Sp^2 I need the variances. Am I trying to use the right test?
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  2. #2
    Lok
    Lok is offline
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    Do sample 1 and sample 2 follow any law? n: # of trials seems like it could be a binomial law? In this case you can find the std deviation with the definition of the variation in a binomiale law (mean = E(x) = np; then find var = np(1-p) => std dev = sqrt(var))

    If you give the whole question it might be easy to figure out
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  3. #3
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    well, here's the original problem:

    An experiment is conducted to determine weather the average dose of vaccine exceeds that of another by .2 mg.

    n1=45
    n2=40
    x1(bar) = #
    x2(bar) = #
    s1 = #
    s1 =#
    alpha/2 = 0.025

    For this I used the z-test. Then question asks to test under same conditions, except that this time, n's are small and population variances are unknown. So how would I approach this?
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  4. #4
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    I am closing this thread, I have just about given up on trying to find a solution to this problem.
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  5. #5
    MHF Contributor matheagle's Avatar
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    what are the hypotheses?
    It seems that you can either do the s pooled test if the pop variances are equal or the uequal case via Satterthwaite,
    see Student's t-test - Wikipedia, the free encyclopedia
    read...

    Equal sample sizes, equal variance
    This test is only used when both:
    the two sample sizes (that is, the n or number of participants of each group) are equal;
    it can be assumed that the two distributions have the same variance.

    AND

    Unequal sample sizes, equal variance
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