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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
- MLv 71 decade agoFavorite 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).