� = � ∑ �. ��� − ∑ � ∑ ���
� ∑ �
2
− ∑ �
2
� = 12 × 861,253
− 78 × 132,637 12 × 650
− 78
2
= −0,006187
ln � =
∑ ��� − � ∑ � �
= 11,0932 � = 65.726,669
�
′
= ��
��
�
′
= 65.726,669 �
−0,006187�
�
′
= 65.726,669 �
−0,0061871
= 65.321,27 ≈ 65.321
���� =
∑ |
��
�
|
� �=1
�
=
2,67 12
= 22,28
2. Metode Kuadratis
KUADRATIS t
y t²
t³ t
⁴ ty
t²y t
yt 1
55.775 1
1 1
55.775 55.775
13 50.951
2
46.583 4
8 16
93.167 186.333
14 59.898
3
51.009 9
27 81
153.027 459.081
15 66.944
4
108.655 16
64 256
434.620 1.738.480
16 72.091
5
74.095 25
125 625
370.474 1.852.369
17 75.338
6
73.288 36
216 1.296
439.725 2.638.350
18 76.686
7
85.789 49
343 2.401
600.525 4.203.673
19 76.134
8
56.958 64
512 4.096
455.664 3.645.312
20 73.683
9
52.868 81
729 6.561
475.812 4.282.308
21 69.331
10
77.089 100
1.000 10.000
770.893 7.708.925
22 63.081
11
55.013 121
1.331 14.641
605.138 6.656.513
23 54.930
12
46.827 144
1.728 20.736
561.918 6.743.016
24 44.880
78
783.948 650
6.084 60.710
5.016.736 40.170.135
222 783.948
� = �� �
2
�
2
− � � �
4
� = 650
2
− 12 × 60.710 = −306.020
Universitas Sumatera Utara
� = � � � � − � � �� � = 78 × 783.948 − 12 × 5.016.736 = 947.112
� = � �
2
� � − � � �
2
�
� = 650 × 783.948 − 12 × 40.170.135 = 27.524.586
� = � � � �
2
− � � �
3
� = 78 × 650 − 12 × 6.084 = −22.308 � = �� ��
2
− � � �
2
� = 78
2
− 12 × 650 = −1.716 � =
�� −�� �� −�
2
= 11.795,578 � =
�−�� �
= -949,808 � =
∑ �−� ∑ �−� ∑ �
2
�
= 40.105,693 �
′
= � + �� + ��
2
�
′
= 40.105,693 + 11.795,578 � + −949,808�
2
�
′
= 40.105,693 + 11.795,5781 + −949,8081
2
=
50.951,46
≈
50.951
���� =
∑ |
��
�
|
� �=1
�
=
2,03 12
= 16,89
Metode Terpilih: Kuadratis
Universitas Sumatera Utara
Verifikasi Peramalan
y yt
e=y-yt |MR|
UCL LCL
55.775 50.951
4.824 -
48.164,67 -48.164,67 46.583
59.898 -13.314 18.137,90
48.164,67 -48.164,67 51.009
66.944 -15.935 2.620,79
48.164,67 -48.164,67 108.655 72.091 36.564
52.499,08 48.164,67 -48.164,67
74.095 75.338
-1.244 37.807,55
48.164,67 -48.164,67 73.288
76.686 -3.399
2.154,94 48.164,67 -48.164,67
85.789
76.134
9.655 13.053,68
48.164,67 -48.164,67 56.958
73.683 -16.725 26.379,70
48.164,67 -48.164,67 52.868
69.331 -16.463 261,16
48.164,67 -48.164,67 77.089
63.081 14.009 30.472,03
48.164,67 -48.164,67 55.013
54.930
82 13.926,35
48.164,67 -48.164,67 46.827
44.880 1.946
1.864,01 48.164,67 -48.164,67
199.177,20
-60.000 -40.000
-20.000 20.000
40.000 60.000
P T
. S
W M
S
Permintaan 683 tahun 2016
Irawan 683 LCL
UCL
Universitas Sumatera Utara
PERAMALAN PRODUK IRAWAN 683-SP – PT. SWMS
Irawan 683-SP Bulan
Demand
Januari
93.060
Februari
76.257
Maret
48.974
April
117.381
Mei
88.140
Juni
110.940
Juli
109.946
Agustus
66.432
September
101.747
Oktober
61.182
November
49.231
Desember
57.885
Total 981.175
Metode Peramalan Terpilih: •
Metode Eksponensial •