Statistics Assignment Help-171502

Assignment 1

(Refer Plots, Summary Output and Data section at end of the assignment)

1.  Refer to plot c and the seasonal exponential data for Sally-Stenography Source.

a. What type of model appropriate for the data? Explain.

b. Use that model, and discuss its efficacy. (How well does it perform?)

c. Offer any suggestions to improve the model performance.

2. The table below features three exponential smoothing models used on the same set of data.

a. Based solely on the information in this output, what would you conclude about the underlying data set? Explain.

b. Are there any other possible explanations for the values in the table? Explain.

For Questions 3 to 9, refer to the attached regression output (refer Plots and Data section). Here we are using years of experience, college GPA, and company entrance score to predict employee salaries at a local firm.

3. We would conclude that the overall model (using all three explanatory variables) is statistically significant at the .05 level.

a. true

b. false

4. None of the explanatory variables are useful predictors

a. true

b. false

5. The most useful predictor in the presence of the other explanatory variables is

6. Multicollinearity is

 i Severe.

ii Mild.

(iii) Nonexistent.

8. Which of the following combinations would be expected to yield the highest pay? Values are years, GPA, and score.

1. 5, 3.7, 80
2. 7, 3.2, 85
3. 8, 3.6, 85
4. 5, 3.8, 85

8. Interpret the coefficient of determination for the overall (3-variable) model.

9. The model in Summary Output 2 uses only entrance score to predict salary.

a. Write the least squares regression equation.

b. Is this a useful model? Explain.

c. Is the output consistent with the other output? Explain.

10. Given the information, which answer is BEST?

1. Model 1 performs the best in all areas.
2. Model 3 performs better than Model 2.

1. We would most likely prefer Model 1.
2. We would most likely prefer Model 2.
3. We would most likely prefer Model 3.

11. Refer again to the Sally-Stenographer data (refer Plots and Data section, at the end) . Use exponential smoothing with a smoothing constant = 0.2. This model

1. is effective
2. is appropriate
3. tends to under predict
4. tends to over predict

12. In the previous problem, suppose we used a different smoothing constant value. This change would

1. generate an appropriate model
2. possibly generate a better model (with respect to prediction)
3. tend to under predict
4. tend to over predict

13. You are tracking mall sales over a two-year period.

1. The data will surely contain a trend component.
2. The data will likely contain a verifiable seasonal component.

14. In Question #13, suppose we track sales over a one-year period.

1. The data will surely contain an irregular (random) component.
2. The data will likely contain a verifiable seasonal component.

15. Discuss how a method on this assignment can be used to catch data errors such as data entry mistakes.

CORRELATION MATRIX