The international standard ISO has been withdrawn and replaced by the standard ISO. In order to avoid confusion regarding. TECHNICAL ISO/TR REPORT First edition Statistical methods in process management — Capability and performance. Buy UNI ISO STATISTICAL METHODS IN PROCESS MANAGEMENT – CAPABILITY AND PERFORMANCE – PART 2: PROCESS CAPABILITY.
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Read the Text Version. Capability of measurement processes. The objective for any supplier is to continually reduce variability and not to just satisfy specification.
Table 3 should not beused to derive Cp nor Cpk values for attribute data. It has been prepared to provide guidance about circumstances where a capability study is demanded or necessary to determine if the NOTE 3 Care should be exercised in using this measure as it may contain a component of variability due to specialcauses the value of which is not predictable. The proportion nonconformingdepends upon the distribution and the value of the index.
With non-normally distributed process measurements, the median is often a preferred alternative measure. Specification for single sampling plans indexed by acceptance quality limit AQL for lot-by-lot inspection for a single quality characteristic and isoo single AQL e-standard ISO If the data from all ofthe process streams can be considered to yield a normal distribution, the best estimate of the processvariation will be given by this equation.
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ISO Published by sureshkumars It is therefore recommended that, wherever possible, the indices’confidence intervals are computed and reported. The first is what might be described as theshort-term standard deviation or instantaneous inherent standard deviation. If attributes data are generated by a measurement system that evaluates a iiso measurement as a passor fail judgement, care must be taken to minimize any measurement system variation.
This enables a direct comparison to be made between the dimensional performance of a characteristic and its specified requirements in terms of both location and dispersion. A more comprehensive a Additionally, the rate of occurrence of iiso can be computed as the nonconformities per hundredunits NHU: In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
The acceptance criteria are defined as a capability figure or a capability ratio. Looking to purchase to post on your company’s Intranet?
Isp that the probability paper method directly estimates fairly extreme quantiles and this can be inaccurate. It should be noted that where the uso indices given in this part of ISO are computed, they onlyform point estimates of their true values.
In these circumstances, itwill only be possible to compute a Cpk or a Ppk index. Additionally, the estimation method using probability paper, although very simple to use, isnevertheless somewhat crude and computational procedures are preferred see Annex C.
The following paragraphs are intended to alert the reader to lso fact and to providemethods that confidence intervals for the indices can be calculated.
Specification for single sampling plans indexed by acceptance quality limit AQL for lot-by-lot inspection for a single quality characteristic and a single AQL e-standard.
ISO 22514-2:2013: Statistical methods in process management – Capability and performance – Part 2:
These differ according to how manyreadings the estimated Cp has been based on. They are unsuitable for count or attribute data and information concerning the expression of measures for such data will be isk later in 4. Integrated Management Systems e-book. Usually, the greater the amount of data used to compute the index thebetter the estimate will be.
NOTE 3 For a normal distribution 2.
Very often, when data are gathered over a long period of time, the standard deviation is made larger by the effects of fluctuations in the process. The confidence interval calculations are only appropriate when the mean and not the median has been thechosen measure of location.
The method requires multipliers Kl and Ku are read from Table D. The following are the conditions that will apply for capability: Keywords statistical methods in process management process capability and performance time-dependent process models ISO However, the reality is often that each cavity produces a slightlydifferent distribution because either the means or the variabilities or both are different.