| Week 2 | Testing means - T-tests |
| | In questions 2, 3, and 4 be sure to include the null and alternate hypotheses you will be testing. |
| | In the first 4 questions use alpha = 0.05 in making your decisions on rejecting or not rejecting the null hypothesis. |
| 1 | Below are 2 one-sample t-tests comparing male and female average salaries to the overall sample mean. |
| | (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.) |
| | 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. |
| | 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? |
| | Males | | | | Females |
| | Ho: Mean salary = | 45.00 | | | Ho: Mean salary = | 45.00 |
| | Ha: Mean salary =/= | 45.00 | | | Ha: Mean salary =/= | 45.00 |
| | Note: While the results both below are actually from Excel's t-Test: Two-Sample Assuming Unequal Variances, |
| | 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. |
| | | Male | Ho | | | Female | Ho |
| | Mean | 52 | 45 | | Mean | 38 | 45 |
| | Variance | 316 | 0 | | Variance | 334.6666666667 | 0 |
| | Observations | 25 | 25 | | Observations | 25 | 25 |
| | Hypothesized Mean Difference | 0 | | | Hypothesized Mean Difference | 0 |
| | df | 24 | | | df | 24 |
| | t Stat | 1.9689038266 | | | t Stat | -1.9132063573 |
| | P(T<=t) one-tail | 0.0303078503 | | | P(T<=t) one-tail | 0.0338621184 |
| | t Critical one-tail | 1.7108820799 | | | t Critical one-tail | 1.7108820799 |
| | P(T<=t) two-tail | 0.0606157006 | | | P(T<=t) two-tail | 0.0677242369 |
| | t Critical two-tail | 2.0638985616 | | | t Critical two-tail | 2.0638985616 |
| | 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. |
| | Is this a 1 or 2 tail test? | | | | Is this a 1 or 2 tail test? | 2 tail |
| | - why? | | | | - why? | Ho contains = |
| | P-value is: | | | | P-value is: | 0.0677242369 |
| Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? | | | | Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? | | No |
| Why do we not reject the null hypothesis? | | | | Why do we not reject the null hypothesis? | | P-value greater than (>) rejection alpha |
| | Interpretation of test outcomes: |
| 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. |
| | (Since we have not yet covered testing for variance equality, assume the data sets have statistically equal variances.) |
| | Ho: | Male salary mean = Female salary mean |
| | Ha: | Male salary mean =/= Female salary mean |
| | Test to use: | t-Test: Two-Sample Assuming Equal Variances |
| |
| | P-value is: |
| | Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
| | Reject or do not reject Ho: |
| If the null hypothesis was rejected, calculate the effect size value: |
| If calculated, what is the meaning of effect size measure: |
| | Interpretation: |
| b. | Is the one or two sample t-test the proper/correct apporach to comparing salary equality? Why? |
| 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.) |
| | Again, please assume equal variances for these groups. |
| | Ho: |
| | Ha: |
| | Statistical test to use: |
| | What is the p-value: |
| | Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
| | Reject or do not reject Ho: |
| If the null hypothesis was rejected, calculate the effect size value: |
| If calculated, what is the meaning of effect size measure: |
| | Interpretation: |
| 4 | Since performance is often a factor in pay levels, is the average Performance Rating the same for both genders? |
| | NOTE: do NOT assume variances are equal in this situation. |
| | Ho: |
| | Ha: |
| | Test to use: | t-Test: Two-Sample Assuming Unequal Variances |
| | | What is the p-value: |
| | Is P-value < 0.05 (one tail test) or 0.25 (two tail test)? |
| | | Do we REJ or Not reject the null? |
| | If the null hypothesis was rejected, calculate the effect size value: |
| | If calculated, what is the meaning of effect size measure: |
| | | Interpretation: |
| 5 | If the salary and compa mean tests in questions 2 and 3 provide different results about male and female salary equality, |
| | which would be more appropriate to use in answering the question about salary equity? Why? |
| | What are your conclusions about equal pay at this point? |