GB/T 14838-1993 Determination of the precision of test methods for rubber and rubber products
Some standard content:
National Standard of the People's Republic of China
Rubber and rubber products
Test method standards
Determination of precision
Rubber and rubber products--Determination of precision for test method standards GB/T 14838-93
This standard refers to the international standard ISO)/TR9272-1986 "Determination of precision for test method standards for rubber and rubber products". 1 Subject content and scope of application
This standard specifies the criteria for determining the precision of test method standards for rubber and rubber products, and gives the format of the precision clauses in the test method standards. Through the Mooney viscosity test of unvulcanized rubber, an example of calculating precision is given. This standard is applicable to the determination of precision in various standard test methods and test method standards for rubber and rubber products. The test method for which the precision is to be determined must have a certain degree of accuracy and be mastered by most laboratories, and the test results can be expressed as quantitative continuous variables. 2 Reference standards
GB3358 Statistical terms and symbols
GB6379 Precision of test methods Repeatability and reproducibility of standard test methods determined by inter-laboratory tests GB/T447.1 Precision of test methods for chemical products Inter-laboratory tests Repeatability and reproducibility of standard test methods GB/T1232 Determination of Mooney viscosity of unvulcanized rubber 3 Terms and symbols
3.1 Terms
3.1.1 Accuracy, deviation, precision. Although this standard does not involve accuracy and deviation, their definitions are also given to illustrate the difference between these two terms and precision.
3.1.1.1 Accuracy
The degree of consistency between the measured mean value of the sample and the true value. Note: ① This true value can be a recognized reference value or standard value; (②) The reference value or standard value can be determined theoretically, or by reference to a recognized standard, another test method, or in some cases, the average value of the numerical (quantity) values obtained by applying the test method to all samples of a batch of materials: ③ The higher the accuracy, the greater the degree of consistency. 3.1.1.2 Bias
The difference between the average value of the test result and the recognized reference value. Note: High accuracy means that the deviation is small or negligible. When there is a deviation, increasing the number of tests does not improve accuracy. It only increases the understanding of the degree of deviation.
3.1.1.3 Precision
precision
The degree of consistency between the results obtained by implementing the test steps multiple times under certain conditions. Note: (i) The degree of consistency is usually the opposite of the standard deviation, and high precision is equivalent to a low (small) standard deviation; State Administration of Technical Supervision approved from December 30, 1993 to October 1, 1994, and implemented GB/T 14838-93. ② High precision and large deviation or low accuracy may exist at the same time. 3.1.2 Terminology adapted to the needs of rubber and rubber product test method standards 3.1.2.1 Determination The test procedure is applied to a specimen to produce a numerical (test) determination value, which is used to form an average or median value. 3.1.2.2 Test result The average or median value of a specified number of determination values. It is the reported value of a test. 3.1.2.3 Level This standard refers to the level of the specimen.
3.1.2.4 Cell
This standard refers to any combination of a laboratory and a level. 3.1.2.5 Repeatability, rrepeatability, r refers to a numerical value. In the same laboratory, by the same operator, using the same test method and equipment, the absolute value of the difference between the test results of the same sample is obtained with a certain specified probability of tolerance. The probability of this standard is 95%. 3.1.2.6 Reproducibility, Rreproducibility, R refers to a numerical value. In different laboratories, different operators, different equipment and within a specified time, the absolute value of the difference between the test results of the same sample is obtained with the same test method with a certain specified probability of tolerance. The probability of this standard is 95%. 3.1.2.7 Short-term repeatability, rsTshort-term repeatability, rstThe repeatability obtained in a shorter time period (such as minutes, hours or hours). Note: Each test method standard needs to be specified. 3.1.2.8 Long-term repeatability, rir long-term repeatability, rt.T Repeatability obtained over a long period of time (such as days, weeks or months). Note: ① Each test method standard needs to be specified. ② Factors affecting long-term repeatability include different operators, different environmental factors (such as different temperatures and humidity caused by seasonal changes) and recalibration or adjustment of equipment.
3.1.2.9 Short-term reprodubility, Rsr Reproducibility obtained in a shorter period of time (in minutes, hours or days). 3.1.2.10 Long-term reproducibility, RLr long-term reproducibility, RLT Reproducibility obtained over a long period of time (such as days, weeks or months). Note: Factors affecting long-term reproducibility include different operators, different environmental factors (such as different temperatures and humidity caused by seasonal changes) and recalibration or adjustment of equipment.
3.1.2.111 Type 1 repeatability and type 1 reproducibility The samples assigned to the laboratory are objects that can be tested immediately or with only a little processing, that is, the repeatability and reproducibility obtained by type 1 and type I samples in 4.2.1.
3.1.2.122 Type 2 repeatability and type 2 reproducibility The samples assigned to the laboratory are some materials that are made into objects that can be tested according to the specified formula composition and process conditions, that is, the repeatability and reproducibility obtained by the sub-type samples in 4.2.1. 3.1.2.13 Relative repeatability (r) and relative reproducibility (R)
The percentage of repeatability r and reproducibility R to the average value of the corresponding level, which is equivalent to the coefficient of variation. rsT or rr represents relative short-term repeatability or relative long-term repeatability. (Rs?) or (RLr) indicates relative short-term reproducibility or relative long-term reproducibility. 3.1.2.14 Acceptance difference (duplicate determinations) refers to a numerical value. The difference between two determinations in the laboratory should be lower than this value with a specified probability. 490
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GB/T 14838-93
Note: ① The two determinations are obtained at the same time using the same sample, operator and equipment without other instructions. The probability is 95%. ② If the calculated difference is lower than the tolerance, the two determinations can be used to average, and the average value is written into the test report as the test result. If the calculated difference exceeds the tolerance, it is necessary to perform another determination to obtain a qualified determination. If another determination is performed, the original determination is invalidated and only the new determination is used as a judgment. 3.1.2.15 Acceptance difference (Xdeterminations) refers to a numerical value. The maximum range of the values measured a specified number of times in the laboratory should be lower than this value with a specified probability. Note: ① The values measured a specified number of times are obtained at the same time using the same sample, operator and equipment without other instructions, with a probability of 95%.
② If the calculated maximum range is lower than the allowable deviation, all measured values can be averaged or median, and the average or median is written into the test report as the test result. If the maximum range exceeds the allowable deviation, a measurement must be carried out to obtain a qualified measurement value. If another measurement is carried out, the original measurement value must be invalidated, and only the new measurement value is used as a judgment. 3.2 Symbols
TS.—Measurement value (is the number of repeated measurements, which can be 1, 2, 3,...)；Y test result, that is, the average or median of α times of measurement value TS; y the average value of indoor repeated test results;
--the average value of the average values of each room at the same level; a certain laboratory;
j--a certain level;
-a certain experiment,
number of laboratories;
number of levels;
level value, the same as Y;
number of repeated tests of indoor test results; range,
square of the maximum range,
S;--the standard deviation of a certain unit test result; S,-repeatability standard deviation;
Skinter-laboratory standard deviation;
Z h)—
the average value of the repeated test results in the room to be tested arranged in order from small to large, h is 1, 2, *·, h; the calculated value of the statistic for testing the suspicious values and outliers of the variance using the Cochran method; the calculated value of the statistic for testing the suspicious values and outliers of the mean using the Dixon method; repeatability;
R——-reproducibility;
(r) relative repeatability, %;
(R)—relative reproducibility, %;
f—a factor that amplifies the range (W) to obtain the allowable error rAp; Pea
-the calculated value of the rent relationship coefficient;
ur or the constant of the linear regression equation of R and m; V--r or the coefficient of the linear regression equation of R and m; 4 General principles
4.1 General principles
4.1.1 This standard does not replace GB6379, but gives the principles for determining the time period of inter-laboratory tests based on the characteristics of the test methods for rubber and rubber products. The applicable part should be selected according to the needs when using it. 4.1.2 Repeatability refers to the degree of consistency of similar test results obtained by the same laboratory under certain specified conditions. Reproducibility refers to the degree of consistency of similar test results obtained by different laboratories under certain specified conditions. If the test results are close to consistency, there is good repeatability or good reproducibility.
4.1.3-The precision of a test method refers to the sensitivity of measuring the basic performance it is intended to measure, and does not necessarily represent the characteristics of a test. Since the test method is not sensitive to basic properties, the precision may also be good. : 4.1.4 Repeatability and reproducibility should be determined under representative laboratory conditions. There is no need to pay too much attention to the uniformity of the experimental conditions and the test samples, which will over-optimize the precision. 4.1.5 The statistical formulas for calculating precision repeatability and reproducibility are listed in GB6379 or GB/T4471. Appendix C and Appendix D of this standard also give the calculation formula in a brief form. 4.2 Determination of specimens for inter-laboratory testing
4.2.1 Three types of specimens for inter-laboratory testing: Type I: fully prepared specimens. Specimens that do not need to be processed before measurement, such as dumbbell specimens for tensile properties tests. Type II: semi-finished specimens. Specimens that need to be slightly processed before measurement, such as dumbbell specimens punched from vulcanized rubber test pieces before tensile properties tests.
Type II: Specimens are prepared according to the specified formula composition and process conditions using specified (number) raw materials. If rubber, vulcanizing agent, carbon black, operating oil and antioxidant are given, they should be mixed, vulcanized and punched into dumbbell-shaped specimens before the tensile performance test. 4.2.2 The type of specimen selected depends on the purpose of the inter-laboratory test. If the consistency of each test equipment is to be evaluated, type 1 or type I specimens should be selected. If the entire test process is to be evaluated, type III specimens should be selected. Type III specimens are of great significance in the acceptance test of raw materials by manufacturers and users. Regardless of type I, type II or type III specimens, they must be distributed to each laboratory from the same source or the same batch, and have good uniformity and homogeneity.
4.2.3 Chemical analysis and general physical tests often do not require or rarely require laboratory preparation before the test of the specimen, and type 1 specimens can be used. To evaluate a certain raw material, such as a test of a certain specified property in rubber or carbon black, it is required to prepare or process the specimen in the laboratory, so type III specimens should be used.
4.2.4 The same raw material should use different types of specimens according to the test method. For example, the quality of styrene-butadiene rubber is determined by the following three tests: a. a chemical analysis, such as measuring the organic acid content; b. a general physical test, such as the Mooney viscosity of raw rubber; c. a performance test, such as tensile strength. The a, b, and c in this list correspond to type I, type I, and subtype specimens, respectively. 4.3 Determination of the time period for indoor repeated tests 4.3.1 There are three types of time periods for repeated tests: a. Very short-term repeated tests are carried out in the shortest possible or very short time period, that is, the same operator uses the same specimen and equipment to perform repeated measurements within a time period of minutes, at most within a time period of hours; b. Short-term repeated tests are carried out in a short time period, that is, the same operator or the same group of operators uses the same specimen and equipment to perform repeated measurements within a time period of days; c. Long-term repeated tests are carried out in a long time period, the time period is measured in weeks or months. In this case, although the same sample is used, different operators or other changes in conditions, such as re-inspection or adjustment of the test equipment, often increase the variability of the repeated test results.
For simplicity, the three time periods of indoor repeated tests are divided into short-term and long-term. Short-term refers to time periods a and b, and long-term refers to time periods ℃.
4.3.2 According to the requirements of the test method standard, the time period of repeated tests in the laboratory shall be specified. 492
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5 Arrangement and requirements for precision inter-laboratory tests
5.1 Inter-laboratory test team
GB/T14838-
The responsible unit that accepts the task of precision determination organizes the inter-laboratory test team and determines the team leader to implement the task. The inter-laboratory test team makes the following preliminary decisions: a. Type of precision: Type 1 or Type 2; b. Time period of repeatability and reproducibility: short-term (minutes, hours, days) or long-term (weeks, months); c. Whether tolerance is required.
5.2 Laboratories and samples
Try to select laboratories that are representative and meet the requirements in terms of different climates and regions. No less than 6 laboratories should participate in the test. If there are less than 6, it is impossible to obtain a reliable evaluation of the reproducibility of the test method. The type and number of samples depend on the range of the tested performance and the variation of precision within this range, the different types of samples that the test method is suitable for, and the possibility of completing the test (such as cost and practical needs, such as commercial or legal precision evaluation). Generally, there should be at least three different levels of samples in the inter-laboratory study, that is, the number of levels should be at least 3. In order to determine the precision of a wide range of applications, there should be five or more different levels of samples, that is, the number of levels should not be less than 5. The samples distributed to each laboratory should be randomly assigned homogeneous materials. A certain amount of reserves must be reserved for each level of samples. When the samples are not homogeneous, it is best to use the same batch of commercial materials and prepare the samples under specified conditions. Storage conditions and handling requirements should be specified for unstable samples. 5.3 Arrangement of inter-laboratory tests
The arrangement of inter-laboratory tests is shown in Table 1. Table 1 lists 9 horizontal specimens and n repeated tests. Each laboratory of each laboratory must conduct q, tests, and the following requirements are met: a. All q, tests should be completed by the same operator or the same group of operators using the same equipment; n tests of the same horizontal specimen must be conducted separately under repeated conditions within a specified time period; b.
Specify the number of repeated tests n. Generally, n is 2 times, and more times can be specified if necessary; c.
q groups of n tests can be conducted on different dates. d.
5.4 Contents of inter-laboratory test report
Test results, the test results should have one more significant digit than that specified in previous practices or test method standards; a.
If the tolerance (AD: or AD) calculation is to be performed, the various measured values of the test results should be listed; b.
Abnormal phenomena during the test;
Date of receipt of the sample and date of the test;
Test equipment conditions.
6 Statistical analysis of precision inter-laboratory test results 6.1 The test results of each laboratory participating in the inter-laboratory test are summarized in the format shown in Table 1. 193
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GB/T14838-93
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6.2 Perform statistical analysis according to Appendix C of this standard. When the number of indoor repeated tests n is greater than 2 or the number of repeated tests in each laboratory is not equal, perform statistical analysis according to Appendix D.
Contents of the precision chapter in the test method standard a.
Is the precision type Type 1 or Type 2?
The time period of repeatability and reproducibility: short-term or long-term? c.
The number of laboratories participating in the test?
d. The number of levels of the sample?
e. The number of repeated tests in the room: equal or unequal repetitions. 7.1 Provide a precision parameter table, the format of which is shown in Table C13 of Appendix C. 7.2 Determine the relationship between repeatability and reproducibility and the level value: whether it is a stable, linear or logarithmic relationship. 7.2.1 If there is a linear relationship, indicate the linear relationship expression. 7.2.2 Make a coordinate graph of repeatability and reproducibility and the level value, see Figure C1 in Appendix C. 7.3 Determine the relationship between relative repeatability and relative reproducibility and the level value, see Figure C2 in Appendix C. 7.4 Repeatability and reproducibility parameters r and R are recommended to provide the following content when applying the standard of test methods for rubber and rubber products: a. The difference between the results of two separate tests on the same specimen under the specified repetitive conditions shall not exceed the repeatability r parameter value more than once in every 20 times;
Under the specified reproducibility conditions, the difference between the results of two separate tests on the same specimen in different laboratories shall not exceed the reproducibility R parameter value more than once in every 20 times.
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GB/T14838-93
Appendix A
Flowchart description of repeatability and reproducibility
(Supplement)
1 This appendix explains the contents of Articles 4.2 and 4.3 in the form of a flow chart. 2 The flow chart given in this appendix is a tensile property test. A2
3 Meaning of the footnote symbols of this annex: A3
ST short-term;
LT long-term;
value produced by a single sample;
AD allowable value (allowed for averaging). For repeatability flow chart, see Figures A1 and A2. A4
For reproducibility flow chart, see Figures A3 and A4. A5
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Each group of TS values produces
one, value
GB/T14838—93
rAD=2 /2Ssv
(TAD)=
2/2ssv
rAin=2/2f ·Wsv
x(100)
X(100)
Note: VASsv value can be determined by previous planning datarsr=2/2SsT
(rsr):
Time period (short term)
2/2SsT
r1.T=2 /2S.T
(rtr)-
Time period (long term)
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1 type repetitive flow chart
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x(100)
x(100)
Mixing process
No. 1 vulcanized test piece
TS.TS..,TS.
Time period (short term)
rst =2 /2sT
(rst)=
2/25sT
GB/T 14838-93
Mixing process
No. 2 vulcanized test piece
TS.TS.\,TS
Time period (long term)
Mixing process
To No. vulcanized test piece
TS.TS...TS
TT=2 /2SLT
X(100)
Figure A22 type repeatability flow chart
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2/2StT
x(100)
Laboratory 1
Time period (short term)
RsT=2 /2SsT
(RsT)=
2/2SsT
GB/T 14838-93
Same batch of vulcanized test specimens or vulcanized test pieces
Laboratory 2
Time period (long term)
RL2 /2St.T
×(100)
(RLT)=
Figure A31 Reproducibility flow chart
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2/2StT
Laboratory:
X(100)
Given level
Laboratory number
Laboratory 1
Mixing processing
Vulcanized test piece No. 1
Time period (short term)
RsT=2/2Ssr
GB/T 14838-93
Raw materials from the same batch
Laboratory 2
Mixing processing
Vulcanized test piece No. 2
Time period (long term)
Rt.r-2 /2Si.T
X(100)
Figure A42 Reproducibility flow chart
Appendix B
Critical value table of each statistic
(Supplement)
Laboratory;
Mixing processing
Vulcanized test piece No. 2
X(100)
Table B1. Critical value of Cochran's maximum variance test Number of test results per unit
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Time period (short term)
rst =2 /2sT
(rst)=
2/25sT
GB/T 14838-93
Mixing processing
No. 2 vulcanized test piece
TS.TS.\,TS
Time period (long term)
Mixing processing
To No. vulcanized test piece
TS.TS...TS
TT=2 /2SLT
X(100)
Figure A22 type repeatability flow chart
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nAll kinds of marking industry materials free download
2/2StT
x(100)
Laboratory 1
Time period (short term)
RsT=2 /2SsT
(RsT)=
2/2SsT
GB/T 14838-93
Same batch of vulcanized test specimens or vulcanized test pieces
Laboratory 2
Time period (long term)
RL2 /2St.T
×(100)
(RLT)=
Figure A31 Reproducibility flow chart
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2/2StT
Laboratory:
X(100)
Given level
Laboratory number
Laboratory 1
Mixing processing
Vulcanized test piece No. 1
Time period (short term)
RsT=2/2Ssr
GB/T 14838-93
Raw materials from the same batch
Laboratory 2
Mixing processing
Vulcanized test piece No. 2
Time period (long term)
Rt.r-2 /2Si.T
X(100)
Figure A42 Reproducibility flow chart
Appendix B
Critical value table of each statistic
(Supplement)
Laboratory;
Mixing processing
Vulcanized test piece No. 2
X(100)
Table B1. Critical value of Cochran's maximum variance test Number of test results per unit
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Time period (short term)
rst =2 /2sT
(rst)=
2/25sT
GB/T 14838-93
Mixing processing
No. 2 vulcanized test piece
TS.TS.\,TS
Time period (long term)
Mixing processing
To No. vulcanized test piece
TS.TS...TS
TT=2 /2SLT
X(100)
Figure A22 type repeatability flow chart
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2/2StT
x(100)
Laboratory 1
Time period (short term)
RsT=2 /2SsT
(RsT)=
2/2SsT
GB/T 14838-93
Same batch of vulcanized test specimens or vulcanized test pieces
Laboratory 2
Time period (long term)
RL2 /2St.T
×(100)
(RLT)=
Figure A31 Reproducibility flow chart
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2/2StT
Laboratory:
X(100)
Given level
Laboratory number
Laboratory 1
Mixing processing
Vulcanized test piece No. 1Www.bzxZ.net
Time period (short term)
RsT=2/2Ssr
GB/T 14838-93
Raw materials from the same batch
Laboratory 2
Mixing processing
Vulcanized test piece No. 2
Time period (long term)
Rt.r-2 /2Si.T
X(100)
Figure A42 Reproducibility flow chart
Appendix B
Critical value table of each statistic
(Supplement)
Laboratory;
Mixing processing
Vulcanized test piece No. 2
X(100)
Table B1. Critical value of Cochran's maximum variance test Number of test results per unit
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