Question

Twenty-one daily responses of stack loss (y) (the amount of ammonia escaping) were measured with air flow x1, temperature x2, and acid concentration x3.

1. Obtain a matrix plot of scatter plots for all pairs of variables using Minitab, and state your conclusion based on this graph. [5 marks]

2. Find a multiple linear regression model for this data using Minitab. [5 marks]

3. Check the significance of the model using ANOVA via Minitab and state your conclusion

   at 5% alpha level. [5 marks]

4. Using best subset method based on adjusted R-squared via Minitab, find the best

   regression model, and explain the result. [2 marks]

5. Using stepwise method, find the best regression model by Minitab and explain the results

   obtained at each step. [3 marks]

y	x1	x2	x3
42	80	27	89
37	80	27	88
37	75	25	90
28	62	24	87
18	62	22	87
18	62	23	87
19	62	24	93
20	62	24	93
15	58	23	87
14	58	18	80
14	58	18	89
13	58	17	88
11	58	18	82
12	58	19	93
8	50	18	89
7	50	18	86
8	50	19	72
8	50	19	79
9	50	20	80
15	56	20	82
15	70	20	91

Answer 1

Relation ship among each pair seems to be linear.