1.1 Consider the regression model developed for the National Football League data in Problem 3.1.

Calculate the PRESS statistic for this model. What comments can you make about the likely predictive performance of this model?

Delete half the observations (chosen at random), and refit the regression model. Have the regression coefficients changed dramatically? How well does this model predict the number of games won for the deleted observations?

Answer in R

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Team	y	x1	x2	x3	x4	x5	x6	x7	x8	x9
1	10	2113	1985	38.9	64.7	4	868	59.7	2205	1917
2	11	2003	2855	38.8	61.3	3	615	55	2096	1575
3	11	2957	1737	40.1	60	14	914	65.6	1847	2175
4	13	2285	2905	41.6	45.3	-4	957	61.4	1903	2476
5	10	2971	1666	39.2	53.8	15	836	66.1	1457	1866
6	11	2309	2927	39.7	74.1	8	786	61	1848	2339
7	10	2528	2341	38.1	65.4	12	754	66.1	1564	2092
8	11	2147	2737	37	78.3	-1	761	58	1821	1909
9	4	1689	1414	42.1	47.6	-3	714	57	2577	2001
10	2	2566	1838	42.3	54.2	-1	797	58.9	2476	2254
11	7	2363	1480	37.3	48	19	984	67.5	1984	2217
12	10	2109	2191	39.5	51.9	6	700	57.2	1917	1758
13	9	2295	2229	37.4	53.6	-5	1037	58.8	1761	2032
14	9	1932	2204	35.1	71.4	3	986	58.6	1709	2025
15	6	2213	2140	38.8	58.3	6	819	59.2	1901	1686
16	5	1722	1730	36.6	52.6	-19	791	54.4	2288	1835
17	5	1498	2072	35.3	59.3	-5	776	49.6	2072	1914
18	5	1873	2929	41.1	55.3	10	789	54.3	2861	2496
19	6	2118	2268	38.2	69.6	6	582	58.7	2411	2670
20	4	1775	1983	39.3	78.3	7	901	51.7	2289	2202
21	3	1904	1792	39.7	38.1	-9	734	61.9	2203	1988
22	3	1929	1606	39.7	68.8	-21	627	52.7	2592	2324
23	4	2080	1492	35.5	68.8	-8	722	57.8	2053	2550
24	10	2301	2835	35.3	74.1	2	683	59.7	1979	2110
25	6	2040	2416	38.7	50	0	576	54.9	2048	2628
26	8	2447	1638	39.9	57.1	-8	848	65.3	1786	1776
27	2	1416	2649	37.4	56.3	-22	684	43.8	2876	2524
28	0	1503	1503	39.3	47	-9	875	53.5	2560	2241