To study short term effects of smoking, a sample of 100 smokers was drawn. Each person was asked to report the average number of cigarettes smoked per day and the number of days absent from work due to health reasons. A regression model was used to study the relationship between numbers of cigarettes smoked on number of days absent from work due to health reasons.

Question 1: If, on average, a person smokes 10 cigarettes a day, on average how many days would you expect that person to be absent from work?

Question 2: What is the correlation coefficient between the number of cigarettes and the number of days absent from work?

Question 3: What percentage of variation in number of days absent from work is explained by the number of cigarettes each smoker smokes?

Question 4: What is the standard deviation of prediction errors for this model?

Cigrattes	Days
63	16
61	15
57	19
56	15
56	17
55	15
55	12
54	15
52	9
52	12
52	6
50	10
49	16
48	19
48	17
47	15
47	11
47	19
46	15
45	18
45	10
45	17
45	12
44	14
44	11
44	22
44	11
43	12
43	10
43	17
43	11
42	21
42	11
42	11
42	15
41	14
41	12
41	9
41	9
41	6
41	13
41	13
40	11
40	9
40	21
40	12
40	11
39	14
39	14
38	12
37	16
37	15
37	16
37	17
37	11
37	10
36	7
36	14
36	9
36	11
35	11
35	6
35	15
35	7
34	11
34	11
34	12
34	6
33	10
32	9
32	7
32	12
31	11
31	8
31	5
30	8
30	9
30	6
30	11
29	6
29	12
29	11
28	11
28	12
28	11
27	11
27	5
26	3
26	8
25	11
25	0
24	12
22	6
20	5
19	6
17	4
17	9
17	7
16	2
15	4