Monthly shampoo sales over three years
t	Yt
1	266
2	145.9
3	183.1
4	119.3
5	180.3
6	168.5
7	231.8
8	224.5
9	192.8
10	122.9
11	336.5
12	185.9
13	194.3
14	149.5
15	210.1
16	273.3
17	191.4
18	287
19	226
20	303.6
21	289.9
22	421.6
23	264.5
24	342.3
25	339.7
26	440.4
27	315.9
28	439.3
29	401.3
30	437.4
31	575.5
32	407.6
33	682
34	475.3
35	581.3
36	646.9