Pertemuan 2 PERENCANAAN & PENGENDALIAN PRODUKSI 04/07/2014. Example of Simple Moving Average. Example of Exponential Smoothing TIN 4113

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1 04/07/204 Peremua 2 PERENCANAAN & PENGENDALIAN PRODUKSI TIN 43 Oule: Meode Peramala: Movg Average & Weghed Movg Average Expoeal Smoohg Double Expoeal Smoohg (Hol s) Wer s Mehod for Tred & Seasoal Problems Error orecas MAD, MSE, MAPE, ME aau Bas Referes: Elsayed, A. Elsayed. Aalss ad Corol of Produco Sysem, Prece Hall Ieraoal, 994. Terse, Rchard J., Prcples of Iveory ad Maerals Maageme, Prece-Hall, 994. Vollma, e al. Maufacurg Plag & Corol Sysem, McGraw-Hll, 997. Pujawa, Demad orecasg Lecure Noe, IE-ITS, 20. Example of Smple Movg Average Week Demad 3-Week 6-Week Example of Expoeal Smoohg Expoeal smoohg ad a cosa model are beg used for forecasg. The smoohed average a he ed of perod zero was 80. The acual demad perod was 04. The smoohg cosa s 0,. Wha s he forecas for perod 2 made a he ed of perod?

2 04/07/204. Apa pegaruh jumlah varas produk erhadap peerapa PPIC pada perusahaa ersebu? 2. Dvs perecaaa produks dar peerb buku Pearso memlk daa sales sebaga berku (dalam 000 u): Tahu Pejuala* Perusahaa mempermbagka uuk megguaka meode expoeal smoohg dega kosaa = 0.2 uuk melakuka forecas. Dasumska bahwa perkraa pejuala pada ahu ke-3 adalah u buku. Lakuka forecas uuk ahu ke-5 hgga ahu ke-7. Apakah meode ersebu lebh epa jka dbadgka dega meode Movg Average? (Aalsa ME, MAD, da MSE-ya).. Jelaska megapa pada meode Expoeal Smoohg dsaraka megguaka la α sebesar 0 < α < 0,5? 2. Jelaska karakersk da kods pegguaa masg-masg error forecas, bas, da rackg sgals dalam melakuka jusfkas meode peramala. 3. Tujukka bahwa pada meode Movg Avearge da Expoeal Smooh aka memlk error yag sama pada saa α = 2 N+. 4. Dkeahu daa permaa secara beruru-uru sebaga berku: 2, 0, 8, da 20. a. Lakuka peramala dega dua meode yag berbeda uuk meeuka jumlah permaa 2 perode ke depa. Defska da euka daa-daa pedukug yag dperluka uuk meode yag aka ada guaka. (Tgka kesula meode da keepaa jawaba aka mempegaruh bobo la). b. Lakuka aalsa uuk meeuka meode maakah yag palg sesua uuk daa ersebu. Jelaska alasaya. Smple Tme Seres Models Movg Average (Smple & Weghed) Expoeal Smoohg (Sgle) Double Expoeal Smoohg (Hol s) Wer s Mehod for Seasoal Problems Smple Movg Average orecas s average of prevous observaos or acuals D : ( D D D Noe ha he pas observaos are equally weghed. Issues wh movg average forecass: All pas observaos reaed equally; Observaos older ha are o cluded a all; Requres ha pas observaos be reaed; Problem whe 000's of ems are beg forecas. D ) 2

3 04/07/204 Weghed Movg Average Expoeal Smoohg orecas s based o pas demad daa, each gve a cera wegh. The oal wegh mus equal o. ( w D w D w D Re-do he above example, usg 3 pas daa, each gve a wegh of 0.5, 0.3, ad 0.2 (larger for more rece daa) ) New orecas = α (curre observao of demad) + (-α) (las forecas) Or = α(d ) + (-α) - Ad - = α(d - ) + (-α) -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 oday 0 ( ) ( ) 2 ( ) 3 Expoeal Smoohg Noes: Oly 2 values (D ad - ) are requred, compared wh for movg average Parameer deermed emprcally (whaever works bes) Rule of humb: < 0.5 = 0. o = 0.3 orecas for k perods o fuure s: k 3

4 04/07/204 Persamaa MA da ES Perbedaa MA da ES Sama-sama megasumska demad bersfa saoary Keduaya ergaug pada 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+) 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: 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 ( )( S T ) Demad Acual orecas Moh Smooh he red forecas T T ( S S ) ( ) T orecas k perods o fuure +k wh base ad red k S kt 4

5 04/07/204 Laha Soal (a = 0,; b = 0,; S = 40; T = 0) Perode Demad Level Tred orecas , , , 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 Expoeal Smoohg w/ Tred ad Seasoaly Smooh he seres forecas S D S ( )(S T ) Cm orecas wh red ad seasoaly k ( S kt ) C k m Smooh he red forecas T T (S S ) ( ) T Smooh he seasoaly forecas C D C S ( ) C m 5

6 04/07/204 Expoeal Smoohg w/ Tred ad Seasoaly Example: The Alpha Corporao has a produc wh seasoal dffereces sales bewee he halves of he year. Sales he frs half of he year are geerally less ha for he secod half of he year. or hs reaso hey ve spl sales from he wo prevous years (7 ad 8) o wo halves ad would lke o use hese wo pars o predc sales he comg year (9). They also feel here s a upward red sales. Sales for he pas wo years were: Year 7 Year 8 rs half () Secod half (S) 0 30 Compay execuves esmaed he red a he ed of year 6 was 5 us per half year (T6S) = 5. The base value a he ed of year 6 (B6S) = 95. Seasoal facors were.05 ad 0.95 for he frs ad secod half of he year, respecvely. (Noe hese facors are se purposely o he oppose of wha hey should be o demosrae how hey ll be correced.) α = 0.3; β = 0,5; γ = 0,5 a. Usg a red ad seasoally ehaced model, forecas each of he four half years, sequeally updag he model a he ed of each half year. b. A he ed of year 8 prepare a forecas for each half year year 9. c. Graph values of he updaed seasoal facor for each half year. orecas Errors e = -p, -D Measures of forecas errors: MAD (/ ) MSE (/ ) MAPE (/ ) 2 e e e / D x00% Mea orecas Error (ME or Bas) Trackg Sgals ME ( D ) Wa ME o be as close o zero as possble -- mmum bas A large posve (egave) ME meas ha he forecas s udershoog (overshoog) he acual observaos Noe ha zero ME does o mply ha forecass are perfec (o error) -- oly ha mea s o arge Also called forecas BIAS Trackg Sgal. Guaya adalah memoor apakah forecas ka bas (cederug ak / uru secara kosse) (Acual demad - - orecas demad) MAD - Trackg Sgal + Aleraf laya, guaka ME (lebh mudah). 6

7 04/07/204 Laha soal: orecas: Comparsos of Mehods Pada dua cooh soal d aas (ES wh red da ES wh red & seasoal): Hug forecas masg-masg soal dega megguaka meode Sgle ES. Hug MAD, MSE, MAPE, ME, da Trackg Sgals masg-masg meode. Aalsa da smpulka hasl perhuga yag ada peroleh. orecas 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) Tugas Baca Peremua 3 - Persapa Maer: Perecaaa Aggregae 7