| Week 4: Identifying relationships - correlations and regression |
| To Ensure full credit for each question, you need to show how you got your results. This involves either showing where the data you used is located |
| or showing the excel formula in each cell. | | | | | Be sure to copy the appropriate data columns from the data tab to the right for your use this week. |
| 1 | What is the correlation between and among the interval/ratio level variables with salary? (Do not include compa-ratio in this question.) |
| | a. Create the correlation table. | | | | | | | | | Use Cell K08 for the Excel test outcome location. |
| | i. | | | | | What is the data input ranged used for this question: |
| | ii. | Create a correlation table in cell K08. |
| | b. Technically, we should perform a hypothesis testing on each correlation to determine |
| | if it is significant or not. However, we can be faithful to the process and save some |
| | time by finding the minimum correlation that would result in a two tail rejection of the null. |
| | We can then compare each correlation to this value, and those exceeding it (in either a |
| | positive or negative direction) can be considered statistically significant. |
| | i. What is the t-value we would use to cut off the two tails? | | | | | | T = |
| | ii. What is the associated correlation value related to this t-value? r = |
| | c. What variable(s) is(are) significantly correlated to salary? |
| | d. Are there any surprises - correlations you though would be significant and are not, or non significant correlations you thought would be? |
| | e. Why does or does not this information help answer our equal pay question? |
| 2 | Perform a regression analysis using salary as the dependent variable and the variables used in Q1 along with |
| | our two dummy variables - gender and education. Show the result, and interpret your findings by answering the following questions. |
| | Suggestion: Add the dummy variables values to the right of the last data columns used for Q1. |
| | What is the multiple regression equation predicting/explaining salary using all of our possible variables except compa-ratio? |
| | a. | What is the data input ranged used for this question: |
| | b. | Step 1: State the appropriate hypothesis statements: | | | | | | | | Use Cell M34 for the Excel test outcome location. |
| | | Ho: |
| | | Ha: |
| | | Step 2: | Significance (Alpha): |
| | | Step 3: | Test Statistic and test: |
| | | | Why this test? |
| | | Step 4: | Decision rule: |
| | | Step 5: | Conduct the test - place test function in cell M34 |
| | | Step 6: | Conclusion and Interpretation |
| | | | | What is the p-value: |
| | | | | What is your decision: REJ or NOT reject the null? |
| | | | | Why? |
| What is your conclusion about the factors influencing the population salary values? |
| | c. | If we rejected the null hypothesis, we need to test the significance of each of the variable coefficients. |
| | | Step 1: State the appropriate coefficient hypothesis statements: | | | | | | (Write a single pair, we will use it for each variable separately.) |
| | | Ho: |
| | | Ha: |
| | | Step 2: | Significance (Alpha): |
| | | Step 3: | Test Statistic and test: |
| | | | Why this test? |
| | | Step 4: | Decision rule: |
| | | Step 5: | Conduct the test |
| | | | Note, in this case the test has been performed and is part of the Regression output above. |
| | | Step 6: | Conclusion and Interpretation |
| | | | Place the t and p-values in the following table |
| | | | Identify your decision on rejecting the null for each variable. If you reject the null, place the coefficient in the table. |
| | | | Midpoint | Age | Perf. Rat. | Seniority | Raise | Gender | Degree |
| | | t-value: |
| | | P-value: |
| | | Rejection Decision: |
| If Null is rejected, what is the variable's coefficient value? |
| | | Using the intercept coefficient and only the significant variables, what is the equation? |
| | | Salary = |
| | d. | Is gender a significant factor in salary? |
| | e. | Regardless of statistical significance, who gets paid more with all other things being equal? |
| | f. | How do we know? |
| 3 | After considering the compa-ratio based results in the lectures and your salary based results, what else would you like to know |
| | before answering our question on equal pay? Why? |
| 4 | Between the lecture results and your results, what is your answer to the question |
| | of equal pay for equal work for males and females? Why? |
| 5 | What does regression analysis show us about analyzing complex measures? |