ISO 3951-5:2006 変数による検査のためのサンプリング手順—パート5：変数による検査のための合格品質限界（AQL）によって索引付けされた順次サンプリング計画（既知の標準偏差） | ページ 6

3.1

inspection by variables

inspection by measuring the magnitude(s) of the characteristic(s) of an item

[SOURCE: ISO 3534-2]

3.2

sampling inspection

inspection of selected items in the group under consideration

[SOURCE: ISO 3534-2]

3.3

acceptance sampling

sampling after which decisions are made to accept or not to accept a lot, or other grouping of product, material or service, based on sample results

[SOURCE: ISO 3534-2]

3.4

acceptance sampling inspection by variables

acceptance sampling (3.3) inspection in which the acceptability of a process is determined statistically from measurements on specified quality characteristics of each item in a sample from a lot

[SOURCE: ISO 3534-2]

3.5

process average

rate at which nonconforming items are generated by a process

3.6

acceptance quality limit

AQL

worst tolerable quality level

[SOURCE: ISO 3534-2]

Note 1 to entry: This concept only applies when a sampling scheme with rules for switching and for discontinuation, such as in ISO 2859-1, ISO 3951-1 or this part of ISO 3951 is used.

Note 2 to entry: Although individual lots with quality as bad as the acceptance quality limit may be accepted with fairly high probability, the designation of an acceptance quality limit does not suggest that this is a desirable quality level. Sampling schemes found in International Standards such as ISO 2859-1, ISO 3951-1 or this part of ISO 3951, with their rules for switching and for discontinuation of sampling inspection, are designed to encourage suppliers to have process averages consistently better than the AQL. Otherwise, there is a high risk that the inspection severity will be switched to tightened inspection under which the criteria for lot acceptance become more demanding. Once on tightened inspection, unless action is taken to improve the process, it is very likely that the rule requiring discontinuation of sampling inspection pending such improvement will be invoked.

3.7

quality level

quality expressed as a rate of occurrence of nonconforming units

3.8

nonconformity

non-fulfilment of a requirement

[SOURCE: ISO 3534-2]

3.9

nonconforming unit

unit with one or more nonconformities

[SOURCE: ISO 3534-2]

3.10

“σ” method acceptance sampling plan

sigma method

acceptance sampling plan by variables using the presumed value of the process standard deviation

Note 1 to entry: Adapted from ISO 3534-2.

3.11

specification limit

limiting value stated for a characteristic

[SOURCE: ISO 3534-2]

3.12

lower specification limit

L

specification limit (3.11) that defines the lower limiting value

[SOURCE: ISO 3534-2]

3.13

upper specification limit

U

specification limit (3.11) that defines the upper limiting value

[SOURCE: ISO 3534-2]

3.14

combined AQL requirement

requirement when both upper and lower limits are specified for the quality characteristic and an AQL is given which applies to the combined percent nonconforming beyond the two limits

Note 1 to entry: The use of a combined AQL requirement implies that nonconformities beyond either specification limit are believed to be of equal, or at least roughly equal, importance to the lack of integrity of the product.

3.15

separate AQL requirement

requirement when both upper and lower limits are specified for the quality characteristic and separate AQLs are given which apply to each limit

Note 1 to entry: The use of separate AQL requirements implies that nonconformities beyond either specification limit are either believed to be of different importance to the lack of integrity of the product or it is desired to control them separately.

3.16

maximum process standard deviation

MPSD

σ_max

largest process standard deviation for a given sample-size code letter and acceptance quality limit (3.6) for which it is possible to satisfy the acceptance criterion for the combined control of double specification limits under all inspection severities (i.e. normal, tightened and reduced) when the process variability is known

Note 1 to entry: The MPSD depends on whether the double specification limits are under combined, separate or complex control, but does not depend on the inspection severity.

Note 2 to entry: Adapted from ISO 3534-2.

3.17

switching rule

instruction within an acceptance sampling scheme for changing from one acceptance sampling plan to another of greater or lesser severity of sampling based on demonstrated quality history

Note 1 to entry: Normal, tightened or reduced inspection, or discontinuation of inspection, are examples of “severity of sampling”.

[SOURCE: ISO 3534-2]

3.18

measurement

set of operations having the object of determining a value of a quantity

[SOURCE: ISO 3534-2]

3.19

leeway

quantity derived from a measured value of an item

Note 1 to entry: In the case of a single lower specification limit and in the case of double specification limits, the leeway is obtained by subtracting the numerical value of the lower specification limit from the measured value. In the case of an upper specification limit, the leeway is obtained by subtracting the measured value from the numerical value of the upper specification limit.

3.20

cumulative leeway

value calculated by summing the leeways obtained from the start of the inspection up to, and including, that of the item last inspected

3.21

cumulative sample size

total number of inspected items, counting from the start of the inspection up to, and including, the item last inspected

3.22

acceptance value for sequential sampling

value derived from the specified parameters of the sampling plan and the cumulative sample size

Note 1 to entry: Whether the lot may yet be accepted is determined by comparing the cumulative leeway with the acceptance value.

3.23

rejection value for sequential sampling

value derived from the specified parameters of the sampling plan and the cumulative sample size

Note 1 to entry: Whether the lot may yet be considered unacceptable is determined by comparing the cumulative leeway with the rejection value.

3.24

responsible authority

concept used to maintain the neutrality of this part of ISO 3951 (primarily for specification purposes), irrespective of whether it is being invoked or applied by the first, second or third party