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testing a hypothesis in statistics with p-value, two tails. HELP please & Thank you!?

I always help you guys with math, now I need a little love! I only know basic statistics and need help with a more qualitative analysis. Here's the data and questions.

Sample mean of student GPAs = 2.73

Sample std dev = .495

Sample n = 25

Test the hypothesis Ho: Mu = 2.5 versus Ha: Mu ≠ 2.5. Calculate the P-value. (Include a sketch with the axis labeled and showing the sample mean). Use a significance level, alpha=0.05, and state your conclusion carefully in terms of GPAs.

Please help with some steps. I will understand it if you help me through the various steps of the analysis. Thanks so much!

1 Answer

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  • M
    Lv 7
    1 decade ago
    Favorite Answer

    ANSWER: Conclusion: H1: μ ≠ μ0 is true with 97.1% confidence

    SINGLE SAMPLE TEST, TWO-TAILED, 6 - Step Procedure for t Distributions, "two-tailed test"

    Step 1: State the hypothesis to be tested.

    H0: μ = μ0

    H1: μ ≠ μ0

    Step 2: Determine a planning value for α [level of significance] 0.05

    Step 3: From the sample data determine x-bar, s and n; then compute

    Standardized Test Statistic: t = ( x-bar - μ0 )/( s/ SQRT(n) )

    x-bar = estimate of the Population Mean (statistical mean of the sample) 2.73

    n = number of individuals in the sample 25

    s = sample standard deviation 0.495

    μ0 = Population Mean 2.5

    significant digits 3

    Standardized Test Statistic t = ( 2.73 - 2.5 )/( 0.495 / SQRT( 25 )) = 2.323

    Step 4: Using Students t distribution, "lookup" the area to the left of t =TDIST( 2.323 , 24 , 2 )

    (if lower-tail test) or to the right of t (if upper-tail test) using Excel

    TDIST(x, n-1 degrees_freedom, 2 tails)

    Step 5: Area in Step 4 is equal to P value 0.029

    based on n -1 = 24 df (degrees of freedom).

    Table look-up value shows area under the 24 df curve outside of t = +/- 2.323 is (approx.)

    probability = 0.029

    Step 6: For P ≥ α, fail to reject H0; and for P < α, reject H0 with

    0.95% confidence in H1

    Conclusion: H1: μ ≠ μ0 is true with 97.1% confidence

    Note: level of significance [α] is the maximum level of risk an experimenter is willing

    to take in making a "reject H0" or "conclude H1" conclusion (i.e. it is the maximum

    risk in making a Type I error).

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