PERENCANAAN & PENGENDALIAN PRODUKSI TIN 4113
Peremua 3 Oule: Meode Peramala: Expoeal Smoohg (Sgle) Double Expoeal Smoohg Wer s Mehod for Seasoal Problems Error Forecas MAD, MSE, MAPE, MFE aau Bas Referes: Elsayed, A. Elsayed. Aalss ad Corol of Produco Sysem, Prece Hall Ieraoal, 1994. Terse, Rchard J., Prcples of Iveory ad Maerals Maageme, Prece-Hall, 1994. Pujawa, Demad Forecasg Lecure Noe, IE-ITS, 2011.
Expoeal Smoohg New Forecas = α (curre observao of demad) + (1-α) (las forecas) Or F = α(d -1 ) + (1-α)F -1 Ad F -1 = α(d -2 ) + (1-α)F -2, ds Sehgga pada model, semua daa hsors erwakl pada forecas erakhr dega bobo yag semak kecl (uuk daa yag semak lama)
Expoeal Smoohg Iclude all pas observaos Wegh rece observaos much more heavly ha very old observaos: wegh Decreasg wegh gve o older observaos 0 1 ( 1 ) ( 1 ) ( 1 ) 2 3 oday
Expoeal Smoohg Noes: Oly 2 values (D ad F -1 ) are requred, compared wh for movg average Parameer deermed emprcally (whaever works bes) Rule of humb: < 0.5 = 0.1 o = 0.3 Forecas for k perods o fuure s: F k F
Persamaa MA da ES Sama-sama megasumska demad bersfa saoary Keduaya ergaug pada 1 la parameer, N pada MA da α pada ES. Kalau ada red, kedua-duaya erlamba dalam merespo Keduaya aka meghaslka dsrbus error yag sama apabla α = 2 / (N+1)
Perbedaa MA da ES MA megakomodaska lebh bayak daa ES haya meympa dua daa: forecas erakhr da acual demad erakhr, sedag MA meympa N daa demad erakhr
Double Expoeal Smoohg Wha happes whe here s a defe red? A redy clohg bouque has had he followg sales over he pas 6 mohs: 1 2 3 4 5 6 510 512 528 530 542 552 Demad 560 550 540 530 520 510 500 490 480 Acual Forecas 1 2 3 4 5 6 7 8 9 10 Moh
Double Expoeal Smoohg Ideas behd smoohg wh red: ``De-red'' me-seres by separag seres from red effecs Smooh seres usual maer usg Smooh red forecass usual maer usg Smooh he seres forecas S S D ( 1)( S 1 T 1) Smooh he red forecas T T ( S S 1 ) (1 ) T 1 Forecas k perods o fuure F +k wh base ad red F k S kt
Laha Soal (a = 0,1; b = 0,1; X1 = 40; T1 = 0) Perode Demad Level Tred Forecas 1 47 40 0 2 42 3 16 4 47 5 38 6 34 7 45 8 50 9 47 10 54 11 40 12 43 13
Expoeal Smoohg w/ Tred ad Seasoaly Apabla ka memlk daa yag megadug pola red maupu seasoaly, ka megguaka model. Prspya, daa ddekomposs mejad 3 baga: Daa dasar Kompoe red Ideks musma Masg-masg kemuda dforecas ersedr dega expoeal smoohg, kemuda dgabug kembal
Expoeal Smoohg w/ Tred ad Seasoaly Smooh he seres forecas S D S (1 )(S 1 T 1) C m Smooh he red forecas T T (S S 1 ) (1 ) T 1 Smooh he seasoaly forecas C C D S (1 ) C m
Expoeal Smoohg w/ Tred ad Seasoaly Forecas F wh red ad seasoaly F k (S 1 kt 1 ) C km
Forecas Errors e = F -p, -D Measures of forecas errors: 100% / ) (1/ ) (1/ ) (1/ 1 1 1 x D e MAPE e MSE e MAD
Mea Forecas Error (MFE or Bas) MFE 1 1 ( D F ) Wa MFE o be as close o zero as possble -- mmum bas A large posve (egave) MFE meas ha he forecas s udershoog (overshoog) he acual observaos Noe ha zero MFE does o mply ha forecass are perfec (o error) -- oly ha mea s o arge Also called forecas BIAS
Trackg Sgals Trackg Sgal. Guaya adalah memoor apakah forecas ka bas (cederug ak / uru secara kosse) 1 1 (Acual demad- - Forecas demad) MAD Aleraf laya, guaka MFE (lebh mudah).
Forecas Mejad Lebh Peg Jka Barag harus ada dulu sebelum pelagga membuuhka (producg he produc before here s a defe demad) I adalah kosep saga medasar dar MTS Perusahaa yag memproduks barag aas dasar MTO dak erlalu ergaug pada ramala Lead me pegadaa / produks pajag (lebh pajag dar waku uggu pelagga) Idusr mobl bsa memperpedek lead me sampa yag bsa doleras oleh pelagga dega megubah ssemya mejad assembly o order (ATO)
Peremua 4 - Persapa Tugas Baca: Ssem Persedaa Meode Q Meode P