How to reject the null hypothesis

Question

Discussion:

Q: A study is performed in a large southern town to determine whether the average weekly grocery bill per four person family in the town is significantly different from the national average. A random sample of the weekly grocery bills of four person families in this town is given

a. Assume that the national average weekly grocery bill for a four person family is $100. Is the sample evidence statistically significant? If so, at what significance levels can you reject the null hypothesis?

b. For which values of the sample mean (ie. average weekly grocery bill) would you decide to reject the null hypothesis at the a = 0.01 significance level? For which values of the sample mean would you decide to reject the null hypothesis at the a = 0.10 level?

Weekly Grocery Bills of Randomly Selected Four-Person Families

Family	Bill
1	108.53
2	109.32
3	91.09
4	107.08
5	90.91
6	93.80
7	116.49
8	102.79
9	103.95
10	95.69
11	96.55
12	91.62
13	102.92
14	93.62
15	108.04
16	106.40
17	112.45
18	114.27
19	103.73
20	105.92
21	114.90
22	106.72
23	97.61
24	92.37
25	79.03
26	82.37
27	95.66
28	89.76
29	125.29
30	122.52
31	111.46
32	93.58
33	98.94
34	91.20
35	95.70
36	102.65
37	106.49
38	93.56
39	97.79
40	103.83
41	121.57
42	87.27
43	100.79
44	109.40
45	116.32
46	90.38
47	80.92
48	85.20
49	94.18
50	81.09
51	110.37
52	107.92
53	88.57
54	113.03
55	93.51
56	110.88
57	94.95
58	108.02
59	97.38
60	100.75
61	101.19
62	113.27
63	102.59
64	88.30
65	93.91
66	105.91
67	76.98
68	113.61
69	102.35
70	113.12
71	90.92
72	124.71
73	87.18
74	106.44
75	109.13
76	97.81
77	108.87
78	108.64
79	112.97
80	87.17
81	97.18
82	98.81
83	90.16
84	114.53
85	108.16
86	104.10
87	108.99
88	97.87
89	111.71
90	92.09
91	98.65
92	107.63
93	107.99
94	99.44
95	93.58
96	102.45
97	102.88
98	100.10
99	113.49
100	107.75