Snapback method:

Stage 1	Stage 2	Stage 3	Stage 1	Stage 2	Stage 3	Stage 1	Stage 2	Stage 3
13.11	3.76	9.62	9.57	10.53	11.36	14.32	13.97	10.55
11.12	14.84	10.10	10.17	13.83	9.64	9.79	11.02	11.42
11.67	15.56	8.72	9.27	11.24	9.77	9.74	12.64	11.27
10.37	9.74	14.61	20.01	49.53	10.02	10.10	14.87	14.69
8.65	11.25	9.85	16.32	10.02	10.00	10.97	16.19	23.95
8.69	11.59	12.79	8.75	18.18	12.41	12.52	9.57	9.94
13.46	10.47	9.77	12.54	16.51	10.69	10.70	11.47	9.45
9.22	13.07	11.42	11.47	35.75	11.67	8.35	14.02	9.70
24.23	19.64	5.92	10.39	14.04	11.52	11.22	24.86	12.02
10.87	13.81	11.50	21.56	16.14	9.79	13.83	8.93	12.33

b.determine the required number of observations for 1 percent precision and confidence level of 68%.