ANSIASQ Z 1 4 Acceptance Sampling Plans q
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ANSI/ASQ Z 1. 4 Acceptance Sampling Plans q Devised in 1942 at Bell Labs q Later became MIL-STD-105 E q ISO-2859 q ANSI/ASQ Z 1. 4 (The American National Standard Institute and American Society for Quality Control Z 1. 4) q Wording & terminology changes q Additional tables added 1
ANSI/ASQ Z 1. 4 q Intended to be used for a continuing series of lots, but may be designed for isolated lots. q Standard provides for single, double, and multiple sampling plans. q ANSI/ASQ Z 1. 4 is also provided for normal, tightened, or reduced inspection. q Plan is specified by the AQL, and sample-size code. 2
ANSI/ASQ Z 1. 4 q Normal inspection is used at the start of inspection with changes being a function of recent quality history. )แผนนใชเมอเรมทำการสมตรวจลอต และสามารถเปลยนการตรวจเปนแบบแผนผอนปรน (Reduced inspection ( หรอเขมงวด (Tightened inspection ( ซงขนอยประวตของคณภาพของสนคาททำการตรวจ ( q Tightened inspection: q Generally used when producer’s recent quality history has deteriorated. ) ใชเมอประวตของคณภาพของสนคาแยมาก ( q Reduced inspection: q Used when the producer’s recent quality history has been exceptionally good. 3
ANSI/ASQ Z 1. 4 4
Sample Size Code Letters Most commonly used 5
Comparison of Inspection levels 6
Example For a lot size of 2000, an AQL of 0. 65%, and an inspection level of III, determine the single sampling plans for normal, tightened, and reduced inspection. 7
ANSI/ASQ Z 1. 4 q Normal, Tightened, and Reduced Inspection q Start with normal inspection q Switching Procedures q Normal to tightened q Institute when 2 out of 5 consecutive lots not accepted on original inspection q Tightened to normal q Institute when 5 consecutive lots accepted q If not, then discontinue inspection under this plan 24 8
ANSI/ASQ Z 1. 4 q Switching Procedures q Normal to reduced q Institute when: (all of the following) q Preceding 10 lots on normal inspection have been accepted q Total nonconforming in preceding 10 samples is less than number identified in Table 10 -5. q Production is at a steady rate q Reduced inspection is considered desirable by responsible authority 25 9
ANSI/ASQ Z 1. 4 q Switching Procedures q Reduced to normal q Institute when: (any of the following) q A lot is not accepted q Sampling procedure terminates with neither acceptance or rejection criteria have been met q Production is irregular or delayed q Other conditions 26 10
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- Cluster random sampling vs stratified
- Cluster sampling advantages and disadvantages
- Research sampling
- Convenience sampling images
- Natural sampling vs flat top sampling