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    Statistics - Hypothesis test exercise

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    A postal researcher wanted to test the theory that a higher response rate is achieved when a postal questionnaire is sent out with a personalized covering letter (A) than when the covering letter is impersonal (B).
    Two random samples of 100 people were selected. When the questionnaires were dispatched, the first sample-received letter A and the second received letter B. The response rates to letter A were 70% and to letter B, 55%.
    a) Do these results provide evidence in support of the theory?
    b) Explain the reasoning behind the test.

    Hint:
    Call the response rate for each sample pA and pB respectively and the number in each sample nA and nB.
    Please utilize and see the Student's t-distribution below. In using the t-table data, assume the number of data [100] corresponds to large distribution of (Infinity) in the table [see next pages, the t-table data].
    Also please notice that this is a case of 2 independent samples from 2 populations. We cannot assume that the variance of the 2 populations are the same [not known], so we should utilize t-distribution formula and include both variances.

    Also, remember that for proportions the equations are similar to the mean differences except proportions are replaced for means.

    The final formula for student's t-test of 2 independent groups with unequal population variances [2 independent samples from 2 populations]
    (X1-bar − X2-bar) − (U (X1-bar - X2bar) )
    S (X1-bar - X2-bar)

    Sample means differences − the 2 population means difference
    Standard error [SE.]of the difference between the sample means
    [Also, this is called standard deviation of the
    difference between the sample means]

    In t-test for proportion of these 2 samples, we use the same formula, but with proportions, i.e.,

    PA− PB
    S.E (PA− PB )

    PA− PB
    S.E (PA− PB )

    Where your S.E (PA− PB ) is =

    Please proceed by setting your HO & H1 and carry the 2 proportion t-test as mentioned above.

    See attachment for detailed description.

    © BrainMass Inc. brainmass.com June 3, 2020, 11:22 pm ad1c9bdddf
    https://brainmass.com/statistics/hypothesis-testing/statistics-hypothesis-test-exercise-276147

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