Question

A real estate agent has collected a random sample of 75 houses that were recently sold in a suburban community. She is particularly interested in comparing the appraised value and recent selling price of the houses in this particular market. Using this sample data below, find a 95% confidence interval for the mean difference between the appraised values and selling prices of the houses sold in this suburban community. Interpret the confidence interval for the real estate agent.

------------------------------------------------

House	Value	Price
1	119.37	121.87
2	148.93	150.25
3	130.39	122.78
4	135.70	144.35
5	126.30	116.20
6	137.08	139.49
7	123.49	115.73
8	150.83	140.59
9	123.48	120.29
10	132.05	147.25
11	148.21	152.26
12	139.53	144.80
13	114.34	107.06
14	140.04	147.47
15	136.01	135.12
16	140.93	140.24
17	132.42	129.89
18	118.30	121.14
19	122.14	111.23
20	149.82	145.14
21	128.91	139.01
22	134.61	129.34
23	121.99	113.61
24	150.50	141.05
25	142.87	152.90
26	155.55	157.79
27	128.50	135.57
28	143.36	151.99
29	119.65	120.53
30	122.57	118.64
31	145.27	149.51
32	149.73	146.86
33	147.70	143.88
34	117.53	118.52
35	140.13	146.07
36	136.57	135.35
37	130.44	121.54
38	118.13	132.98
39	130.98	147.53
40	131.33	128.49
41	141.10	141.93
42	117.87	123.55
43	160.58	162.03
44	151.10	157.39
45	120.15	114.55
46	133.17	139.54
47	140.16	149.92
48	124.56	122.08
49	127.97	136.51
50	101.93	109.41
51	131.47	127.29
52	121.27	120.45
53	143.55	151.96
54	136.89	132.54
55	106.11	114.33
56	137.54	141.32
57	134.33	83.76
58	127.59	118.20
59	137.44	140.20
60	114.09	113.55
61	145.46	156.52
62	141.90	137.35
63	116.34	110.61
64	149.20	153.69
65	141.81	153.33
66	116.44	111.95
67	137.74	143.46
68	144.70	142.13
69	149.66	155.46
70	118.17	135.44
71	137.66	127.30
72	119.70	113.77
73	143.12	141.11
74	129.91	130.08
75	141.78	139.35

Answer 1

House	Value	Price	Difference
1	119.4	121.87	-2.5
2	148.9	150.25	-1.32
3	130.4	122.78	7.61
4	135.7	144.35	-8.65
5	126.3	116.2	10.1
6	137.1	139.49	-2.41
7	123.5	115.73	7.76
8	150.8	140.59	10.24
9	123.5	120.29	3.19
10	132.1	147.25	-15.2
11	148.2	152.26	-4.05
12	139.5	144.8	-5.27
13	114.3	107.06	7.28
14	140	147.47	-7.43
15	136	135.12	0.89
16	140.9	140.24	0.69
17	132.4	129.89	2.53
18	118.3	121.14	-2.84
19	122.1	111.23	10.91
20	149.8	145.14	4.68
21	128.9	139.01	-10.1
22	134.6	129.34	5.27
23	122	113.61	8.38
24	150.5	141.05	9.45
25	142.9	152.9	-10.03
26	155.6	157.79	-2.24
27	128.5	135.57	-7.07
28	143.4	151.99	-8.63
29	119.7	120.53	-0.88
30	122.6	118.64	3.93
31	145.3	149.51	-4.24
32	149.7	146.86	2.87
33	147.7	143.88	3.82
34	117.5	118.52	-0.99
35	140.1	146.07	-5.94
36	136.6	135.35	1.22
37	130.4	121.54	8.9
38	118.1	132.98	-14.85
39	131	147.53	-16.55
40	131.3	128.49	2.84
41	141.1	141.93	-0.83
42	117.9	123.55	-5.68
43	160.6	162.03	-1.45
44	151.1	157.39	-6.29
45	120.2	114.55	5.6
46	133.2	139.54	-6.37
47	140.2	149.92	-9.76
48	124.6	122.08	2.48
49	128	136.51	-8.54
50	101.9	109.41	-7.48
51	131.5	127.29	4.18
52	121.3	120.45	0.82
53	143.6	151.96	-8.41
54	136.9	132.54	4.35
55	106.1	114.33	-8.22
56	137.5	141.32	-3.78
57	134.3	83.76	50.57
58	127.6	118.2	9.39
59	137.4	140.2	-2.76
60	114.1	113.55	0.54
61	145.5	156.52	-11.06
62	141.9	137.35	4.55
63	116.3	110.61	5.73
64	149.2	153.69	-4.49
65	141.8	153.33	-11.52
66	116.4	111.95	4.49
67	137.7	143.46	-5.72
68	144.7	142.13	2.57
69	149.7	155.46	-5.8
70	118.2	135.44	-17.27
71	137.7	127.3	10.36
72	119.7	113.77	5.93
73	143.1	141.11	2.01
74	129.9	130.08	-0.17
75	141.8	139.35	2.43
		Mean =	(0.376)	=AVERAGE(D2:D76)
		SD =	9.184	=STDEV.S(D2:D76)
		t value95%	1.9925	=TINV(0.05,74)