A Simple Approach for Monitoring Business Service Time Variation

Table 15

(a) The new service times from the first ten counters in a bank branch (𝜆₁=𝜆₂=0.2). (b) The new service times from the last ten counters in a bank branch (𝜆₁=𝜆₂=0.2).

(a)

𝑡	𝑋1	𝑋2	𝑋3	𝑋4	𝑋5	𝑋6	𝑋7	𝑋8	𝑋9	𝑋10	𝑀𝑡	EWMA𝑀𝑖
1	3.54	0.01	1.33	7.27	5.52	0.09	1.84	1.04	2.91	0.63	1	3.11
2	0.86	1.61	1.15	0.96	0.54	3.05	4.11	0.63	2.37	0.05	0	2.49
3	1.45	0.19	4.18	0.18	0.02	0.70	0.80	0.97	3.60	2.94	0	1.99
4	1.37	0.14	1.54	1.58	0.45	6.01	4.59	1.74	3.92	4.82	1	1.79
5	3.00	2.46	0.06	1.80	3.25	2.13	2.22	1.37	2.13	0.25	0	1.43
6	1.59	3.88	0.39	0.54	1.58	1.70	0.68	1.25	6.83	0.31	1	1.35
7	5.01	1.85	3.10	1.00	0.09	1.16	2.69	2.79	1.84	2.62	0	1.08
8	4.96	0.55	1.43	4.12	4.06	1.42	1.43	0.86	0.67	0.13	0	0.86
9	1.08	0.65	0.91	0.88	2.02	2.88	1.76	2.87	1.97	0.62	0	0.69
10	4.56	0.44	5.61	2.79	1.73	2.46	0.53	1.73	7.02	2.13	1	0.75

(b)

𝑡	𝑋11	𝑋12	𝑋13	𝑋14	𝑋15	𝑋16	𝑋17	𝑋18	𝑋19	𝑋20	𝑉𝑡	EWMA𝑉𝑖
1	5.01	3.88	4.18	0.88	4.06	3.05	4.59	0.63	6.83	0.25	0	1.15
2	1.59	0.19	0.39	0.54	1.73	1.42	4.11	1.25	7.02	0.62	0	0.92
3	1.59	0.65	1.43	1.00	5.52	1.16	4.11	1.37	3.6	2.62	0	0.74
4	3.54	0.65	1.43	1.00	4.06	6.01	4.59	1.37	1.97	0.31	0	0.59
5	5.01	0.01	1.54	7.27	0.09	2.88	4.11	0.97	7.02	0.63	0	0.47
6	4.96	0.14	0.91	4.12	4.06	6.01	2.69	0.63	2.13	0.13	0	0.38
7	4.96	2.46	1.54	7.27	0.45	1.42	0.53	0.63	2.13	4.82	0	0.30
8	1.37	0.44	1.33	1.00	0.45	2.46	2.22	2.87	7.02	4.82	0	0.24
9	1.59	0.01	0.91	1.58	0.54	1.70	1.84	2.79	2.91	0.62	0	0.19
10	5.01	0.44	0.91	0.88	1.73	3.05	1.43	1.74	6.83	4.82	0	0.15