Analysis Control
A. PENDAHULUAN B. ACCEPTANCE SAMPLING Control Analysis
Pengendalian dan pengawasan mutu untuk mengetahui kesesuaian dengan standar tidak dapat diterapkan pada semua produk karena jumlah produk sangat banyak
Analysis Control
Sampling: adalah proses penarikan contoh atau unit sampel baik dari suatu lot barang maupun dari suatu proses produksi.
Pengukuran ktiteria mutu dilakukan hanya terhadap unit contoh yang ditarik dari lot atau proses produksi Penimbangan Pengukuran tebal Analisa lainnya
Analisis dan pengukuran terhadap contoh yang ditarik menghasilkan informasi yang digunakan untuk perbandingan dengan standar guna memutuskan status: penerimaan (accept) penolakan (reject) negosiasi (negotiate) terhadap barang atau proses dari mana contoh tersebut diperoleh
Acceptance sampling adalah prosedur sampling berdasarkan tabel yang memuat ukuran contoh (sample size) dan kriteria penerimaan (acceptance criteria) Tabel tersebut memuat: Acceptance quality level Inspection level Lot size Sample size Acceptance number atau acceptance criteria
Suatu lot barang yang jumlahnya 4801 s/d 24000, harus ditarik sampel dari padanya sebanyak 13 Lot ditolak bilamana setelah analisis 13 sampel tersebut, terdapat lebih dari 2 sampel yang tidak sesuai standar mutu
Acceptance sampling plan A plan (usually a table) stating the number of sample units to be included in the sample as well as the corresponding acceptance and rejection criteria Lot A collection of units (products) that are offered for examination for determination of compliance during a single work shift and are of the same item description, weight range, date of acceptance, etc.
Sample The collective number of sample units for the examination of a lot Sample-size (n) The number of sample units which are to be included in the sample Sample-unit An individual item (roast, chop, steak, etc.) or designated quantity of product to be part of a sample Defect Any nonconformance of any unit of product with specified requirements
Random-sampling A process of selecting a sample from a lot whereby each unit in the lot has an equal chance of selection Acceptable Quality Level (AQL) The maximum number of defects per defined quantity that, for the purposes of sampling inspection, can be considered satisfactory as a process average. Acceptance-number (c) The number in a sampling plan that indicates the maximum number of defects permitted in a sample in order to consider a lot as meeting a specific AQL.
Example 1: A lot consists of 1200 cases, packed 12 x 2.0 lb primary containers per case. A decision is made to use Inspection Level I with AQL = 6.5, since the goods are not in dispute and there is no history of controversy over quality. A container is taken to be the sample unit (2.0 lb each sample) Lot Size (N) = 1200 x 12 or 14,400 units Container Size = 2.0 lb
Example 1: 2.0 lb primary container packed 12 x 2.0 lb per case (secondary container) A lot consists of 1200 cases
Sample size (n) = 13 Acceptance Number (c) = 2 Hasil Analisa = 2 tidak sesuai standar. Decision criteria: if there are no more than two (2) defectives in a sample size of 13 containers the entire lot (14,400 unit) is considered acceptable. KESIMPULAN : Accept the Lot
SEANDAINYA 3 YANG TIDAK SESUAI STANDAR? If, however, there are three (3) or more defectives in the sample the lot is considered as failing to meet the requirements A defective as used in the sampling plans should be defined very clearly, for example: defectives = non-conformance with standard
Jumlah sampel yang ditarik (n=13) dari lot (N=14400),ditarik secara acak Contoh penarikan contoh acak menggunakan Excel N = Nomor 1 s/d 14.400
Example 2: Acceptance sample plan untuk uji mikrobiologi produk hasil laut seperti: Θ Fresh and frozen fish Θ Precooked breaded fish Θ Frozen raw crustaceans Θ Frozen cooked crustaceans Seperti yang direkomendasikan ICMSF (1986).
Recommended microbiological limits for fish and fish products (ICMSF, 1986). Product n 1 c 2 Σ Bacteria/g or / cm 2 m 3 M 4 Fresh and frozen fish 5 3 5 x 10 5 10 7 Precooked breaded fish 5 2 5 x 10 5 10 7 Frozen raw crustaceans 5 3 10 6 10 7 Frozen cooked crustaceans 5 2 5 x 10 5 10 7
n 1 c 2 m 3 M 4 = = = = Number of representative sample units Maximum number of acceptable sample units with bacterial counts between m and M Maximum recommended bacterial counts for good quality products Maximum recommended bacterial counts for marginally acceptable quality products
Example 2: Dalam pemeriksaan mutu mikrobiologi frozen fish, dilakukan penarikan contoh dari suatu lot produksi. Hasil pemeriksaan laboratorium menunjukkan hasil sbb: No. Sampel 1 2 3 4 5 Jumlah bakteri 10E4 5x 10E5 10E6 10E6 10E3
Decision criteria berdasarkan Acceptance sampling ICMSF: n = 5 c = 3 m = 5 x 10E5 M = 10E7 Pertanyaan: Example 2: 1. Apakah produk tersebut pass ataukah reject? 2. Jika produk tersebut pass termasuk kelas mutu apakah produk tersebut, good quality products ataukah marginally acceptable quality?
Example 2: Jawab: 1. Produk tersebut pass atau dapat diterima dan memenuhi standar 2. Produk tersebut termasuk kelas mutu good quality products karena terdapat 3 sampel yang kandungan bakterinya tidak lebih besar dari 5 x 10E5, yaitu sampel no. 1, 2 dan 5 Example 3: Apabila analisa mikrobiologi memberikan hasil seperti tabel berikut :
No. Sampel 1 2 3 4 5 Jumlah bakteri 10E4 5x 10E5 10E6 10E6 10E7 Maka, produk tersebut pass atau dapat diterima dan memenuhi standar namun termasuk kelas mutu marginally acceptable quality products karena terdapat 3 sampel yang kandungan bakterinya tidak lebih besar dari 10E7 namun lebih besar 5x10E5, yaitu sampel no. 3, 4 dan 5
1. ICMSF, 1986 Recommended microbiological limits for fish and fish products. 2. MIL-STD-1916 : 1 April 1996 3. MIL-HDBK-1916: 10 February 1999