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Scope

1.1 This practice covers simple methods for calculating how many units to include in a random sample in order to estimate with a specified precision, a measure of quality for all the units of a lot of material, or produced by a process. This practice will clearly indicate the sample size required to estimate the average value of some property or the fraction of nonconforming items produced by a production process during the time interval covered by the random sample. If the process is not in a state of statistical control, the result will not have predictive value for immediate (future) production. The practice treats the common situation where the sampling units can be considered to exhibit a single (overall) source of variability; it does not treat multi-level sources of variability.

Significance and Use

This practice is intended for use in determining the sample size required to estimate, with specified precision, a measure of quality of a lot or process. The practice applies when quality is expressed as either the lot average for a given property, or as the lot fraction not conforming to prescribed standards. The level of a characteristic may often be taken as an indication of the quality of a material. If so, an estimate of the average value of that characteristic or of the fraction of the observed values that do not conform to a specification for that characteristic becomes a measure of quality with respect to that characteristic. This practice is intended for use in determining the sample size required to estimate, with specified precision, such a measure of the quality of a lot or process either as an average value or as a fraction not conforming to a specified value.

Keywords

Empirical knowledge; Error analysis; Maximum tolerable error; Process control; Sampling data analysis/statistics; Size/size distribution analysis; Statistical methods; Calculating test values; ICS Number Code 03.120.30 (Application of statistical methods)

To find similar documents by ASTM Volume:

14.01 (Healthcare Informatics)

14.02 (General Test Methods; Forensic Psychophysiology; Forensic Sciences; Terminology; Conformity Assessment; Statistical Methods; Nanotechnology; Forensic Engineering; Manufacture of Pharmaceutical Products)

To find similar documents by classification:

03.120.30 (Application of statistical methods)

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