Sampling procedures and tables for isolated lot inspection by attributes
Some standard content:
National Standard of the People's Republic of China Sampling procedures and tables for isolated lot inspection by allribules 1 Subject content and applicable scope GB/T15239 This standard specifies the procedures and implementation methods for sampling inspection by allribules with the number of defective products per 100 units as the quality indicator. It is applicable to the inspection of isolated lots.
2 Reference standards
GB2828 Sampling procedures and sampling tables for batch inspection (applicable to inspection of continuous batches) GB/T3358 General terms
GB10111 Methods of random sampling using random numbers GB/T 6583ISO 8402 Quality—Terms
3 Terms and symbols
3.1 Terms
3.1.1 Unit product
The basic unit divided for the needs of sampling inspection is called unit product. For example, a single product, a pair of products, a group of products, a component or a product of a certain length, a certain area, a certain volume, and a certain weight. It may or may not be consistent with the unit product specified for procurement, sales, production and shipment. 3.1.2 Inspection lot
A certain number of unit products produced under consistent conditions and submitted for inspection. 3.1.3 Isolated batch
Batch separated from the batch series that has been produced or collected and not included in the current inspection batch series. 3.1.4 The number of unit products contained in the approved batch. 3.1.5 Sample unit
The unit product selected from the batch for inspection is called the sample unit. 3.1.6 Sample
The whole of the sample units is called the sample.
3.1.7 Sample tray
The number of sample units contained in the sample is called the sample size. 3.1.8 Unqualified
The unit product quality characteristics do not meet the requirements and are called unqualified. Nonconformity indicates the importance of unit product quality according to quality characteristics, or CB/T 15239-94 approved by the State Bureau of Technical Supervision on October 5, 1994 and implemented on June 1, 1995, or classified according to the severity of nonconformity of quality characteristics. Nonconformity is generally divided into Class A nonconformity, Class B nonconformity and Class C nonconformity. 3.1.9 Class A nonconformity
The extremely important quality characteristics of the unit product do not meet the requirements, or the quality characteristics of the unit product do not meet the requirements seriously. It is called Class A nonconformity
3.1.10 Class nonconformity
The important quality characteristics of the unit product do not meet the requirements, or the quality characteristics of the unit product do not meet the requirements seriously. It is called Class B nonconformity.
3.1.11C-type nonconformityWww.bzxZ.net
The general quality characteristics of a unit product do not meet the requirements, or the quality characteristics of a unit product do not meet the requirements slightly, which is called a (class nonconformity.
3. 1. 12Nonconformity
A unit product with one or more nonconformities is called a nonconformity. According to the nonconformity type, it can be generally divided into Class A nonconformity, Class B nonconformity, and Class C nonconformity.
3.1.13A-type nonconformity
A single product with one or more Class A nonconformities, and may also have Class B and (or) Class nonconformities, is called a Class A nonconformity
3.1.14B-type nonconformity
A unit product with one or more Class B nonconformities, and may also have Class C nonconformities, but does not contain Class A nonconformities, is called a Class B nonconformity.
3. 1. 15C-type nonconformity
A unit product with one or more Class B nonconformities, and may also have Class C nonconformities, but does not contain Class A nonconformities, is called a Class B nonconformity.
3. 1. 15C-type nonconformity
A unit product with one or more Class B nonconformities, and may also have Class C nonconformities, but does not contain Class A nonconformities, is called a Class B nonconformity. Class C defective products
Unit products with one or more Class C defectives, but excluding Class A and Class B defectives, are called Class C defective products. 3.1.16 Number of defective products per 100 units of products The total number of all defective products in the batch divided by the batch size and then multiplied by 100 is called the number of defective products per 100 units of products. That is: number of defective products per 100 units of products The total number of defective products in the batch × 100
3.7.17 Batch quality
The quality of the inspection batch (expressed by the number of defective products per 100 units of products) is called batch quality. 3.1.18 Limit quality
For isolated batches, in order to conduct sampling inspection, limit the quality level to a certain low probability of acceptance. 3.1.19 Inspection
Use measurement, test or other methods to separate the unit products from The process of comparing technical requirements is called inspection. 3.1.20 Counting inspection
Determining whether a unit product is qualified or unqualified based on a group or items of technical requirements specified in the product technical standards is called tolerance inspection.
3.1.21 Qualified judgment number
Make a batch qualified judgment. The maximum number of qualified products allowed in the sample is called the qualified judgment number. 3.1.22 Unqualified judgment number
Make a batch unqualified judgment. The minimum number of unqualified products allowed in the sample is called the unqualified judgment number. 3.1.23 Judgment number combination
The qualified judgment number and the unqualified judgment number or the qualified judgment number series and the unqualified judgment number series are called the judgment array. 3.1.24 Sampling plan
GB/T 15239 94
The combination of the sample size or sample size series and the judgment array is called a sampling plan. 3.1.25 Sampling procedure
The process of using the sampling plan to judge whether the batch is qualified or not is called a sampling procedure. 3-1.26 Single sampling method
The sampling plan composed of the sample size and the judgment array (R) is called a primary sampling plan. 3.1.27 Secondary sampling plan
The sampling plan composed of the first sample size 1, the first sample size n and the judgment array (AA;R, R,) is called a secondary sampling plan.
3.1.28 Inspection level
The corresponding relationship between the batch size of the inspection batch and the sample size is called the inspection level. 3.1.29 Sample size code
The sample size code determined according to the batch size of the inspection batch and the inspection level is called the sample size code. 3.1.30 Batch acceptance probability
For a batch with known quality, the probability of accepting the batch according to a given sampling plan. 3.1.31 Average sample size
For a batch with known quality, the average number of sample units required for inspection according to a given sampling plan to make a qualified or unqualified judgment on the batch is called the average sample size.
3.1.32 Random inspection characteristic curve (C curve)
The relationship curve between the batch acceptance probability determined by a given sampling plan and the batch quality is called the random inspection characteristic curve. 3.2 Symbols
N. Batch completed.
2: Sample size
Note: When it is necessary to distinguish the first sample and the first sample, add the full code 1,2 respectively. For example: represents the first sample size. 1r: qualified judgment number,
R: unqualified judgment number.
Note: when it is necessary to distinguish the first, second, qualified and unqualified judgment numbers, change the code and c to 1.2 respectively. For example, A represents the second qualified judgment number and R represents the first and unqualified judgment numbers.
(A,R): The determination array of the second sampling plan. (ArAgRi+R): The determination array of the second sampling plan.
IL.Q limit quality.
P: Batch acceptance probability.
ASN: Average sample size.
IL: Test level.
4 Inspection procedure
The inspection procedure specified in this standard is as follows:
Specify the quality characteristics of unit products:
Specify the classification of non-conformities;
Specify the limit quality level,
Specify the sampling mode:
Specify the inspection level:
Composition and proposal of inspection batches:
Select the type of inspection plan;
h, search the sampling plan;
Capture samples:
Inspect samples:
Judge whether the batch is qualified or unqualified:
Disposition after batch inspection.
5 Implementation of inspection
5.1 Specify the quality characteristics of single products
GB/T15239—94
In the order form of product technical standards, it is necessary to clearly specify the technical performance, technical indicators, appearance and other qualities or characteristics of the unit product. 5.2 Classification of non-conformities
According to actual needs, non-conformities can be divided into three categories: A, B and (. If necessary, non-conformities can be divided into more than three categories. In addition, in the case of unit products being relatively single, non-conformities can also be divided into two categories, creating a category without distinction.
5.3. Provision of limit quality
In product technical standards or ordering agreements, the limit quality should be determined by negotiation between the ordering party and the supplier. The limit quality can be specified in different ways for non-conforming products. In principle, different limit qualities are specified according to the classification of non-conforming products. The limit quality specified for Class A should be less than the limit quality specified for Class R, and the limit quality specified for Class B should be greater than the limit quality specified for Class R. In addition, it is possible to consider specifying the limit quality for some or a single non-conforming product in the same class, or to consider specifying the limit quality between different categories.
5.4 Selection of sampling mode
This standard provides two modes to meet the requirements of two different situations that are often encountered. 5.4.1 Mode A
When both the producer and the user believe that the batch is isolated, use mode A. 5.4.2 Mode H
For a certain inspection batch, When the producer considers a batch as part of a continuous batch and the user receives it as an isolated batch, mode B is used. 5.5 Provision of inspection level (mode B)
This standard gives three general inspection levels in Tables 2 to 11: S1, S2, S3, and S4, and four special inspection levels: S1, S2, S3, and S4. When the required discrimination power is relatively low, the general inspection level can be specified; when the required discrimination power is relatively high, the general inspection level can be specified. Special inspection levels are only applicable when smaller samples must be used and a greater risk of misjudgment can or must be allowed. 5.6 Formation and submission of inspection batches
Unit products are formed into inspection batches by simple aggregation, or they can be formed into inspection batches in other ways. Inspection batches can be combined with production batches, sales batches, and transportation batches. The batches are the same or different. Normally each inspection batch should be composed of unit products of the same model, grade, type (size, characteristics, composition, etc.), production conditions and production time costs. The composition of the batch, the batch size and the method of proposing and identifying the batch should be determined by negotiation between the supplier and the ordering party. If necessary, the supplier shall provide a suitable storage place for each batch submitted for inspection, provide the equipment required for identification and proposing, and the personnel required for management and sampling. 5.7 Selection of sampling plan type
This standard. Tables 1 to 12 give two types of sampling plans, primary and secondary: For a given group limit quality and inspection level, different types of sampling plans can be used, and the management costs of corresponding sampling plans of various types can be compared. In the case of a sampling plan with a certain number of qualified judgments, there is no corresponding secondary sampling plan. The average sample size of the secondary sampling plan is less than the sample size of the corresponding secondary sampling plan. In addition, the secondary sampling plan is usually higher than the corresponding sampling plan.
However, the limit quality and inspection level specified in the standard are consistent. Regardless of the type of corresponding sampling plan used in this standard for inspection, the discrimination power of the batch quality is basically the same as that of the batch quality.
5.8 Retrieval of sampling plan
5.8.1 Retrieval of sampling plan of model A
5.8.1.1 Retrieval of secondary sampling plan
Inspection·Secondary sampling plan uses Table 1,
GB/T 1523994
Example 1: In the factory sampling inspection of a certain product, the sampling plan of GB/T15239 model A is used to determine LQ-32. Find the first sampling plan when N-1 000. Look up Table 1 and you can get the sampling plan:
5.8.1.2 Test factor of the first sampling plan
Retrieve. : The second sampling plan uses Table 12. Example 2: Under the same conditions as Example 1, if the second sampling plan is used, look up Table 12 and you can get the sampling plan: =20
Ai-2
5.8.2 Test factor of the sampling plan of model B
Retrieve the sampling plan in Tables 2 to 12 based on the determined inspection level and limit quality level. 5.8.2.1 Retrieval of the primary sampling plan
Based on the determined test level and limit quality level, search for the sampling plan in Tables 2 to 11. Example 3. In the factory sampling inspection of a certain product, the sampling plan of GB/T15239 Model B is adopted. If ILQ=32 is specified, if the special inspection level S-2 is used to find the primary sampling plan when N=1000, the corresponding plan can be obtained by looking up Table 11:
Example 4: Under the same conditions as Example 3, if the general inspection level 1 is used, the corresponding plan can be obtained by looking up Table 11: n—50
5.8.2.2 Retrieval of the primary sampling plan
Use Table 12 to search for the secondary sampling plan.
5.9 Sample selection
Samples should be randomly selected from the inspection batch. Methods such as GB10111 can be used to conduct simple random selection in the entire inspection batch. Sampling methods such as stratified proportional random sampling can also be used as appropriate. When using the secondary sampling method, each sample should be selected from the entire batch. The time to draw samples can be during the formation of the batch or after the batch is formed. 5.70 Sample inspection
For each inspection item specified in the light, according to the inspection methods and sample qualification criteria specified in the relevant standards and technical requirements, each sample in the sample should be inspected one by one to count the number of unqualified products in the inspected sample. When unqualified products are classified, they should be accumulated separately. 5.11 Method for judging whether a batch is qualified or unqualified 5.71.1 Case of single throw sampling scheme
After determining a sampling scheme based on the limit quality inspection level, according to the results of the sample inspection, if the number of unqualified products found in the sample is less than or equal to the qualified judgment number, the batch is judged to be a qualified batch. If the number of unqualified products found in the sample is greater than or equal to the unqualified judgment number, the batch is judged to be an unqualified batch.
5.11.2 Situation of two sampling plans
After the sampling plan is determined according to the limit quality and the test level, according to the results of the sample inspection, if the number of unqualified products found in the first sample is less than or equal to the first qualified judgment number, the batch is judged to be a qualified batch; if the number of unqualified products found in the first sample is greater than or equal to the first unqualified judgment number, the batch is judged to be an unqualified batch. GB/T 15239--- 94
If the number of unqualified products found in the first sample is greater than the first qualified judgment number but less than the first unqualified judgment number, the second sample is drawn for inspection. If the sum of the number of unqualified products found in the first and second samples is less than or equal to the second qualified judgment number, the batch is judged to be a qualified batch. If the sum of the number of unqualified products found in the third and fourth samples is greater than or equal to the second unqualified judgment number, the batch is judged to be an unqualified batch.
5.12 Treatment after batch inspection
The qualified batches shall be accepted as a whole batch, and the ordering party may propose certain additional conditions to the supplier on the basis of negotiation. The unqualified batches shall be returned to the supplier in principle or the supplier and the ordering party shall negotiate to resolve. For the products that have passed the batch inspection and are temporarily put into production but have not been delivered to the ordering party immediately: if they are stored in the warehouse for more than a certain period of time (the specific time shall be specified in the product technical standards or order form), they must be re-inspected and delivered to the ordering party only after they pass the inspection. For the batches that fail the re-inspection, they shall be treated as the whole batches submitted for inspection again, and the unqualified products shall be submitted for inspection again
Regardless of whether the batch products are accepted or rejected, and whether the unqualified products are part of the sample, as long as they are unqualified products found during the inspection, the ordering party has the right to refuse to accept them. The rejected unqualified products can be repaired or corrected, and can be submitted for inspection again in the prescribed manner with the consent of the ordering party.
b. Delivery of non-conforming batches
The supplier shall conduct a detailed inspection on the non-conforming batches and shall repair the non-conforming products found before resubmitting them for inspection.
Which level of sampling plan shall be used for the batches submitted for inspection? Whether to inspect all types of non-conformities or only inspect the individual types of non-conformities in the selected batches shall be determined by the ordering party. 6 The sampling characteristic curve of the sampling plan (C curve: Figure 10 of this standard gives (×: The curve is based on Poisson/one distribution. The actual operating characteristics will have better discrimination than these curves, that is, when the indicated acceptance probability is greater than or equal to 0.00, there is a greater acceptance probability, and when the indicated acceptance probability is less than 0.1, there is a smaller acceptance probability.
GB/T15239--94
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