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Thread: Can a Z-Test of Two Sample means in Excel be used to answer two separate hypotheses?

  1. #1
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    Red face Can a Z-Test of Two Sample means in Excel be used to answer two separate hypotheses?

    Can a Z-Test of Two Sample means in Excel be used to answer two separate hypotheses.
    1) Hypothesized Mean Difference=0 (Two-Tailed) (NULL vs Alternate, ho = ha)
    2) Treatment > Control (One-Tailed)
    I am currently doing a Z-Test of Two Sample Means (Control vs Treatment) with Null and Alternate Hypotheses. This is used to determine if there is statistical evidence to indicate a difference between the two means using the Two Tail approach.

    Question 1

    Can I use the same Z-Test of Two Sample Means output from Excel to Answer Hypothesis 2 above ie Treatment > Control OR is a t-Test: Two-Sample Assuming Equal Variances the more valid approach.

    Question 2

    Does it matter if the sample populations vary e.g. n=100 (Treatment) vs n=50 (Control) with either tested hypothesis


    1. Current Logic Hypothesis 1.

    If z < z Critical two-tail WE CANNOT REJECT the NULL HYPOTHESIS

    And/or if P(Z<=z) two-tail > 0.05 WE CANNOT REJECT the NULL HYPOTHESIS


    If z > z Critical two-tail WE CAN REJECT the NULL HYPOTHESIS / Accept Alternate Hypothesis
    And/or if P(Z<=z) two-tail < 0.05 WE CANNOT REJECT the NULL HYPOTHESIS


    1. Proposed Logic Hypothesis 2. Where Treatment > Control else FALSE Treatment < Control

    Z-Statistic < Critical One Tail Value Therefore CANNOT REJECT the NULL HYPOTHESIS
    Then Check PValue for 1 Tail > 0.05 Therefore CANNOT REJECT the NULL HYPOTHESIS


    Z-Statistic > Critical One Tail Value Therefore REJECT the NULL HYPOTHESIS
    Then Check PValue for 1 Tail < 0.05 Therefore REJECT the NULL HYPOTHESIS



    Thankyou for your time in advance
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  2. #2
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    Re: Can a Z-Test of Two Sample means in Excel be used to answer two separate hypothes

    Can a Z-Test of Two Sample means in Excel be used to answer two separate hypotheses?-statsdualtests.jpg

    This is an image of the two test outputs. I am simply trying to achieve 2 objectives (Ho=Ha and Ht > Hc) with one test method ie Ztest
    For some reason Excel Data Analysis formulas switch the Variance positions to opposite for Z and T Test ??? as shown in the image
    Last edited by XGIS; Jan 19th 2019 at 03:44 PM. Reason: Extra Info, Question Clarity
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