Week 2 |
Testing means – T-tests |
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In questions 2, 3, and 4 be sure to include the null and alternate hypotheses you will be testing. |
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In the first 4 questions use alpha = 0.05 in making your decisions on rejecting or not rejecting the null hypothesis. |
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1 |
Below are 2 one-sample t-tests comparing male and female average salaries to the overall sample mean. |
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(Note: a one-sample t-test in Excel can be performed by selecting the 2-sample unequal variance t-test and making the second variable = Ho value – a constant.) |
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Note: These values are not the same as the data the assignment uses. The purpose is to analyze the results of t-tests rather than directly answer our equal pay question. |
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Based on these results, how do you interpret the results and what do these results suggest about the population means for male and female average salaries? |
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Males |
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Females |
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Ho: Mean salary = |
45.00 |
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Ho: Mean salary = |
45.00 |
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Ha: Mean salary =/= |
45.00 |
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Ha: Mean salary =/= |
45.00 |
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Note: While the results both below are actually from Excel’s t-Test: Two-Sample Assuming Unequal Variances, |
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having no variance in the Ho variable makes the calculations default to the one-sample t-test outcome – we are tricking Excel into doing a one sample test for us. |
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Male |
Ho |
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Female |
Ho |
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Mean |
52 |
45 |
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Mean |
38 |
45 |
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Variance |
316 |
0 |
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Variance |
334.667 |
0 |
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Observations |
25 |
25 |
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Observations |
25 |
25 |
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Hypothesized Mean Difference |
0 |
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Hypothesized Mean Difference |
0 |
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df |
24 |
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df |
24 |
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t Stat |
1.968903827 |
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t Stat |
-1.91321 |
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P(T<=t) one-tail |
0.03030785 |
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P(T<=t) one-tail |
0.03386 |
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t Critical one-tail |
1.71088208 |
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t Critical one-tail |
1.71088 |
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P(T<=t) two-tail |
0.060615701 |
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P(T<=t) two-tail |
0.06772 |
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t Critical two-tail |
2.063898562 |
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t Critical two-tail |
2.0639 |
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Conclusion: Do not reject Ho; mean equals 45 |
Conclusion: Do not reject Ho; mean equals 45 |
Note: the Female results are done for you, please complete the male results. |
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Is this a 1 or 2 tail test? |
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Is this a 1 or 2 tail test? |
2 tail |
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– why? |
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– why? |
Ho contains = |
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P-value is: |
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P-value is: |
0.06772 |
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Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
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Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
No |
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Why do we not reject the null hypothesis? |
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Why do we not reject the null hypothesis? |
P-value greater than (>) rejection alpha |
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Interpretation of test outcomes: |
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2 |
Based on our sample data set, perform a 2-sample t-test to see if the population male and female average salaries could be equal to each other. |
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(Since we have not yet covered testing for variance equality, assume the data sets have statistically equal variances.) |
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Ho: |
Male salary mean = Female salary mean |
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Ha: |
Male salary mean =/= Female salary mean |
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Test to use: |
t-Test: Two-Sample Assuming Equal Variances |
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P-value is: |
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Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
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Reject or do not reject Ho: |
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If the null hypothesis was rejected, calculate the effect size value: |
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If calculated, what is the meaning of effect size measure: |
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Interpretation: |
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b. |
Is the one or two sample t-test the proper/correct apporach to comparing salary equality? Why? |
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3 |
Based on our sample data set, can the male and female compas in the population be equal to each other? (Another 2-sample t-test.) |
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Again, please assume equal variances for these groups. |
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Ho: |
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Ha: |
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Statistical test to use: |
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What is the p-value: |
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Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
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Reject or do not reject Ho: |
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If the null hypothesis was rejected, calculate the effect size value: |
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If calculated, what is the meaning of effect size measure: |
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Interpretation: |
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4 |
Since performance is often a factor in pay levels, is the average Performance Rating the same for both genders? |
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NOTE: do NOT assume variances are equal in this situation. |
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Ho: |
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Ha: |
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Test to use: |
t-Test: Two-Sample Assuming Unequal Variances |
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What is the p-value: |
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Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
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Do we REJ or Not reject the null? |
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If the null hypothesis was rejected, calculate the effect size value: |
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If calculated, what is the meaning of effect size measure: |
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Interpretation: |
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5 |
If the salary and compa mean tests in questions 2 and 3 provide different results about male and female salary equality, |
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which would be more appropriate to use in answering the question about salary equity? Why? |
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What are your conclusions about equal pay at this point? |
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