Question

Part 1: Model Building

1. Submit both this word and excel file

2. Keep two decimal places for your answer

Using the data Reynolds.xls. The variables are defined as:

Sales (Y) =number of electronic laboratory scales sold

Months (X) =the number of months the salesperson has been employed

1. Develop the scatter plot using Sales as y axis and Months as x axis, and can you see the curvature?

2. Using a simple linear regression model to develop an estimated regression equation to predict the Sales. What is the adjusted-R square?

3. Using a second-order regression model to develop an estimated regression equation to predict the Sales. What is the adjusted-R square? (Hint: second-order regression model should look like: y=b0+b1X+b2X2, and we learnt it in Chapter 16)

4. Compare the adjusted-R square from 2 and 3, which one is larger? Which model is better? (Hint: we learn this in Chapter 15)

5. Use 4 diagrams to test the 5 model assumptions for the second-order regression model. Do you think they are violated? (Hint: we learn this in week 12 computer skill class)

Months	Sales
41	275
106	296
76	317
104	376
22	162
12	150
85	367
111	308
40	189
51	235
9	83
12	112
6	67
56	325
19	189

Answer 1