ASTM D3244 Standard Practice for Utilization of Test Data to Determine Conformance with Specifications
1. Scope
1.1 This practice covers guidelines with which two parties, usually a supplier and a receiver, can compare and combine independently obtained test results whenever there is a product quality dispute.
1.2 This practice defines a technique for comparing an assigned test value with a specification limit.
1.3 This practice applies only to those test methods which specifically state that the repeatability and reproducibility values conform to the definitions herein.
2. Referenced Documents
2.1 ASTM Standards:
D1319 Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
E 29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
2.2 ISO Standard:
ISO 4259 Determination and Application of Precision Data in Relation to Methods of Test
3. Terminology
3.1 Definitions:
3.1.1 acceptance limit (AL), n - a numerical value that defines the point between acceptable and unacceptable quality.
3.1.1.1 Discussion - The AL is not necessarily the specification limit. It is a value that takes into account the specification value, the test method precision, and the confidence level desired for defining minimum acceptable quality relative to the specification value.
3.1.2 assigned test value (ATV), n - the average of all results obtained in the several laboratories which are considered acceptable based on the reproducibility of the test method.
3.1.3 determination, n - the process of carrying out the series of operations specified in the test method whereby a single value is obtained.
3.1.4 dispute, n - when there is a question as to product quality because a test value obtained falls outside the acceptance limit.
3.1.5 operator, n - a person who normally and regularly carries out a particular test.
3.1.6 precision, n - the degree of agreement between two or more results on the same property of identical test material. In this practice, precision statements are framed in terms of the repeatability and reproducibility of the test method.
3.1.7 receiver, n - any individual or organization who receives or accepts the product delivered by the supplier.
3.1.8 repeatability (r), n - quantitative expression of the random error associated with a single operator in a given laboratory obtaining replicate results with the same apparatus under constant operating conditions on identical test material within a short period of time. It is defined (3.1.8.1) as that difference between two such single results as would be exceeded in the long run in only 1 case in 20 in the normal and correct operation of the test method (3.1.8.3). (This is known as the 95 % confidence level.)
3.1.8.1 Discussion - The repeatability and reproducibility values should have been determined according to the methods described in ASTM Research Report RR:D02-1007, Manual on Determining Precision data for ASTM Methods of Petroleum Products and Lubricants or ISO 4259.
3.1.8.2 Discussion - Not all standards organizations define repeatability and reproducibility in precisely these same terms, and attention should always be paid to definitions before comparing precision values quoted.
3.1.8.3 Discussion - This difference is related to the repeatability or the reproducibility standard deviation but is not the standard deviation.
3.1.9 reproducibility (R), n - quantitative expression of the random error associated with operators working in different laboratories, each obtaining single results on identical test material when applying the same method. It is defined (3.1.8.1) as that difference between two such single and independent results as would be exceeded in the long run in only 1 case in 20 in the normal and correct operation of the test method. See 3.1.8.3.
3.1.10 result, n - the value obtained by following the complete set of instructions of a test method. It may be obtained from a single determination or several determinations, depending on the instruction of the test method.
3.1.11 supplier, n - any individual or organization responsible for the quality of a product just before it is taken over by the receiver.
3.1.12 test sample, n - a portion of the product taken at the place where the product is exchanged, that is, where the responsibility for the product quality passes from the supplier to the receiver. Actually, this is rarely possible and a suitable sampling location should be mutually agreed upon.
3.1.13 true value (µ), n - for practical purposes, the value towards which the average of single results obtained by N laboratories tends, when N becomes very large (3.1.13.1). Consequently, such a true value is associated with the particular test method employed.
3.1.13.1 Discussion - It is recognized that there are cases where a true value not equal to the method average can exist. As used in this practice, the method average value is intended to mean "true value" even if the method is biased.
