Single Sampling n c Double Sampling n 1

ชนดของแผนการสมตวอยาง Single Sampling (n, c) Double Sampling (n 1, c 1, n 2, c 2) Multiple Sampling (n 1, c 1, n 2, c 2, …) Sequential Sampling (item-by-item)

การสมตวอยางเชงคณลกษณะ n sampling Inspect & count number of defectives Acceptance number c N Reject lot Accept lot

����� ����� AQL = Acceptable Quality Level -Poorest quality level for vendor process which Producer thinks that Consumer would accept as process average. )��������������������� �� 100 ����

����� (��� ( LTPD = Lot Tolerance Percent Defective -Poorest quality level for vendor process which Consumer thinks they would accept as process average. )��������� ������������������� lot

����� (��� ( AOQ = Average Outgoing Quality (��������� ) -% of outgoing non-conforming that pass the process to consumers (���������� Lot ������������ ) -AOQ is approximately = Pa p (Pa ���������

���� ��� AOQLทควรร = Average Outgoing Quality Limit ����� - A limitation of outgoing quality level = Max (AOQ)

����� (��� ( ATI = Average Total Inspection - Total amount of inspection required by sampling program when Rectifying Inspection is applied

����� (��� ( N = Lot or Batch Size n D x, d = = = C, Ac Re = = Sample Size No. of Defectives (NC) per lot No. of Defectives (NC) found in a sample acceptance number rejection number

SINGLE SAMPLING PLAN Start - Take a sample of size n - Count no. of NC (d) Accept lot d>c Reject lot

OC Definitions on the Curve 100% a = 0. 10 75% 50% b = 0. 10 LTPD 25% AQL Probability of Accepting Lot 90% Go od . 03 Indifferent. 06 Bad. 09 Lot Quality (Fraction Defective)

Slide 20

• Advantage of a double-sampling plan over single sampling is that it may reduce total amount of required inspection • Suppose first sample in a double-sampling plan is smaller than for a singlesampling plan • If lot is accepted or reject on first sample, cost of inspection is lower • Also possible to reject a lot without completing inspection of second sample

MULTIPLE SAMPLING PLAN (����������� ( ���������� DOUBLE SAMPLING PLAN���������� (������� 2 ตวอยาง ����� ) Cumulative Sample Size 20 40 60 80 100 120 140 Acceptance Number 1 3 5 8 9 10 Rejection Number 4 5 6 8 10 11 11

Operation – Characteristic Funtion (OC Curves for xbar) จาก L คอ กำหนดใหใชขดจำกดควบคม Sigma เชน (3 Sigma) K คอ Sigma ทเปลยนแปลงไป n คอ Sample Size คอ Standard normal cumulative distribution function(เปดตาราง Z)

B K