Results of Proficiency Test Rubber/Compounds May 2005

Transcription

1 Results of Proficiency Test Rubber/Compounds May 25 Organised by: Spijkenisse, the Netherlands Authors: ing. R.J. Starink Correctors: R. Agten & dr. R.G. Visser Report: iis5p2 June 25

2 CONTENTS 1 INTRODUCTION SET UP ACCREDITATION PROTOCOL SAMPLES ANALYSES RESULTS STATISTICS GRAPHICS Z-SCORES EVALUATION EVALUATION PER TEST PERFORMANCE EVALUATION FOR THE GROUP OF LABORATORIES COMPARISON OF THE PROFICIENCY TEST OF MAY 25 WITH PREVIOUS PT S DISCUSSION... 1 Appendices: 1. Data and statistical results List of participants Abbreviations and literature iis5p2 page 2 of 32

3 1 INTRODUCTION Since 2, the organised a proficiency test for the analysis of Rubber and Compounds. As part of the annual proficiency test program of 24/25, the Institute decided to continue this proficiency test on Rubber and Compounds. In this international interlaboratory study, 2 laboratories from 13 different countries have participated. See appendix 2 for the number of participants per country. In this report the results are presented and discussed. 2 SET UP The in Spijkenisse was the organiser of this proficiency test. It was set up in close co-operation with analytical experts in the field of rubber. It was decided to organise a true type proficiency test to evaluate the participant's laboratories against the precision statements in the literature (ISO and ASTM). In order to be able to measure the curing by the individual laboratories, it was decided to send cured and uncured material. Thus for this round 3 different samples were prepared: one raw rubber (type Isoprene rubber), one pre-cured sample (vulcanised slabs) and a participant-cured sample. The participants were asked to report the analytical results using the indicated units on the report form. 2.1 ACCREDITATION The in Spijkenisse, the Netherlands, is accredited in agreement with ISO-guide 43 and ILAC G13:2, since January 2, by the Dutch Accreditation Council (Raad voor Accreditatie). 2.2 PROTOCOL The protocol followed in the organisation was the one as described for proficiency testing in the report i.i.s. Interlaboratory Studies: Protocol for the Organisation, Statistics and Evaluation of November 23 (i.i.s.-protocol, version 3.). 2.3 SAMPLES All samples were obtained from a Dutch rubber laboratory. A bale of raw rubber was cut into pieces of ±1 kg. One may assume that this bale is homogeneous and as it was produced in one batch, no homogeneity testing was performed. The samples were labelled 529. One compound was prepared and divided in two parts. One half was cured to Tc = 95 in accordance with ASTM D5289:1. This batch was labelled 53. The other half part of the compound had to be vulcanised by the participants in accordance with ASTM D5289:1 and this was labelled 531. iis5p2 page 3 of 32

4 The compound was made as follows: component parts per hundred parts of rubber Polymer (Isoprene) 1. remarks Carbon Black 35. IRB-7 Sulphur 2.25 Stearic acid 2. Zinc Oxide 5. TBBS.7 table 1: recipe of the compounds of #53 and #531 The compound was checked for homogeneity. The homogeneity of the compound for samples #53 and #531 was checked by measurements of Vulcanisation characteristics with the Moving Die Rheometer (MDR) for Minimum Torque Ml, Mh, Cure times Tc 5 and Tc 9 in accordance with ASTM D5289:1 on 7 stratified random selected samples. See the following tables for the test results. Sample Ml in dnm Mh in dnm Tc 5 in min Tc 9 in min sample sample sample sample sample sample sample table 2: homogeneity test of the compound of #53 and 531 From the results in table 1 the repeatabilities of the results were calculated by multiplication of the standard deviations by 2.8: Ml in dnm Mh in dnm Tc 5 in min. Tc 9 in min. observed repeatability in % r (D5289:1 C) in % table 3: comparison of repeatabilities of the results of table 2 with literature values The repeatability of the results of the homogeneity tests were in agreement with requirements of ASTM D5289:1 (compound C). Therefore, homogeneity of the samples was assumed. The three samples 529, 53 and 531 were sent to the participating laboratories on April 6, 25. iis5p2 page 4 of 32

5 2.4 ANALYSES The participants were asked to determine by applying the analysis procedure that is routinely used in the laboratory on: - Sample 529: Mooney Viscosity (MML + UML) - Sample 53: Tensile Strength, Modulus 1%, 2% and 3%, Elongation at break, Tear Test and Hardness. - Sample 531: Abrasion Test, Density, Hardness, Tensile Strength, Modulus 1%, 2% and 3%, Elongation at break and Vulcanisation Characteristics (MDR and ODR). To get comparable results a detailed report form, was sent together with each set of samples. Also a letter of instructions was sent along. 3 RESULTS During four weeks after sample despatch the results of the individual laboratories were gathered. The original data are tabulated in the appendices of this report. The laboratories are presented by their code numbers. Directly after the deadline, a reminder fax was sent to those laboratories that had not yet reported. Shortly after the deadline the available results were screened for suspect data. A result was called suspect in case the Huber Elimination Rule (a robust outlier test, see lit.5) found it to be an outlier. The laboratories that produced these suspect data were asked to check the results. Additional or corrected data are placed under 'Remarks' in the result tables in appendix 1. A list of abbreviations used in the tables can be found in appendix STATISTICS Statistical calculations were performed as described in the report i.i.s. Interlaboratory Studies: Protocol for the Organisation, Statistics and Evaluation of August 1998 (iis98protocol, version 2.) For the statistical evaluation the unrounded (when available) figures were used instead of the rounded results. Results reported as < or > were not used in the statistical evaluation. Before further calculations, the normality of the distribution of the various data sets per determination was checked by means of the Lilliefors-test. In the case of an anormal distribution, the statistical evaluation should be used with care. According to ISO 5725 (1986 and 1994, lit.7 and 8) the original results per determination were submitted subsequently to Dixon s and Grubbs' outlier tests. Outliers are marked by D(.1) for the Dixon s test, by G(.1) or DG(.1) for the Grubbs test. Stragglers are marked by D(.5) for the Dixon s test, by G(.5) or DG(.5) for the Grubbs test. Both outliers and stragglers were not included in the calculations of averages and standard deviations. iis5p2 page 5 of 32

6 Finally the reproducibilities were calculated from the standard deviations by multiplying them with a factor of GRAPHICS In order to visualise the data against the reproducibilities from literature, Gauss plots were made, using the sorted data for one determination (see appendix 1). On the Y-axis the results from a component in a sample are plotted. The corresponding laboratory numbers are under the X-axis. A continuous horizontal line presents the average of the reported data. The target reproducibility limits of the selected standard are presented by two dotted lines parallel to the average line at (average - target reproducibility) and at (average + target reproducibility). Outliers and other data, which were excluded from the calculations, are represented as a cross. All other data are represented as a triangle. Furthermore, Kernel Density Graphs were made. This is a method for producing a smooth density approximation to a set of data that avoids some problems associated with histograms (see appendix 3; nr.11 and 12) 3.3 Z-SCORES To evaluate the performance of the participating laboratories the z-scores were calculated. As it was decided to evaluate the performance of the participants in this proficiency test (PT) against the literature requirements, e.g. ASTM reproducibilities, the z-scores were calculated using a target standard deviation. This results in an evaluation independent of the spread of this interlaboratory study. The target standard deviation was calculated from the literature reproducibility by division with 2.8. The z-scores were calculated in accordance with: z (target) = (result - average of proficiency test) / target standard deviation Absolute values for z<2 are very common and absolute values for z>3 are very rare. Therefore the usual interpretation of z-scores is as follows: z < 1 good 1 < z < 2 satisfactory 2 < z < 3 questionable z > 3 unsatisfactory 4 EVALUATION During the execution of this proficiency test no problems occurred. All participants reported results. Not all laboratories were able to perform all analyses requested. In total the 2 reporting laboratories reported 286 numerical results. Observed were 14 outlying results, which is 4.9% of the numerical results. In proficiency studies outlier percentages of 3 % % are quite normal. Not all data sets proved to have a normal distribution. Anormal distributions were found for sample 529; Mooney Viscosity UML, for sample 53; Modulus 1%, Elongation at iis5p2 page 6 of 32

7 break and Hardness and for sample 531; Hardness and MDR Ts1. In these cases the statistical evaluation should be used with due care. One can see that this is justified from the corresponding Kernel Density Graphs. 4.1 EVALUATION PER TEST In this section the results are discussed per test. All results and the statistical results, reported on the tests are summarised in appendix 1. Mooney Viscosity: The determinations for MML and UML are problematic for one laboratory. In total only two results were outside the reproducibility limits. The calculated reproducibility for MML and UML are, after rejection of the statistical outliers, in good agreement with the requirements of ISO289:94. Tensile Strength: For both samples (53 and 531), this determination is problematic for one laboratory. For each sample only one result was outside the reproducibility limits. The calculated reproducibilities are for both samples, after rejection of the statistical outliers, in full agreement with the requirements of ASTM D412:2. Unfortunately ISO37 gives no precision data. Furthermore, it is noticed that the RSD(53) is smaller then the RSD(531), 7.1 vs 7.5%, which is expected. Mod.1,2&3%: This determination was not problematic. For modulus 1% of sample 53, only one result was outside the reproducibility limits. The calculated reproducibility is, after rejection of the statistical outlier, in agreement with the requirements of ASTM D412:2. For modulus 1% of sample 531, again only one result was outside the reproducibility limits. The calculated reproducibility is, after rejection of the statistical outlier, in agreement with the requirements of ASTM D412:2. For modulus 2% and 3% (sample 53 and 531) no target precision data are available. It is noticed that the RSD s for all the Modulus of sample 53 are smaller then the RSD s of sample 531 as expected. The relative spreads are for all three tests significantly different. The precision data of the High Tensile NR were used (see also table 1 and 2 of ASTM D412:98). Elongation at Break: This determination is problematic for both samples. For the pre-cured sample 53 as well for the cured sample 531, one result was outside the reproducibility limits and the calculated reproducibility is not at all in agreement with the requirements of ASTM D412:2. Tear Test: This determination very problematic. One result was just outside the reproducibility limits. The calculated reproducibility is not at all in agreement with the requirements of ISO34:94. iis5p2 page 7 of 32

8 Hardness: Abrasion Test: Density: This determination is not problematic. Only for sample 53 (pre-cured sample) a result was outside the reproducibility limits. The calculated reproducibilities of both samples (53 and 531) are, after rejection o f the statistical outliers, in agreement with the requirements of ISO48:94. As more and other labs reported a result for sample 53, it is not remarkable that RSD(53) is larger then RSD (531). (2.7% vs 1.3%), although it is unexpected. This determination is very problematic. Four out of six results were outside the reproducibility limits. The calculated reproducibility is, after rejection of the statistical outlier, not at all in agreement with the requirements of the draft-iso4649. This determination is problematic for one laboratory. The spread is, after rejection of the statistical outlier, relatively small. Unfortunately no target precision data is available. MDR Vulca.char: Some analytical problems were observed. In total six results were outside the reproducibility limits. Only the calculated reproducibilities of Ml and Tc9 were in agreement with the requirements of ASTM D5289:1. The calculated reproducibilities for Ml, Mh and Ts1 were not in agreement. For Ts2, Tc1, Tc25 and Tc95 no target precision data are available. One participant measured his values with a Goettfert Elastograph and not with a MDR/ODR. ODR Vulca.char: No conclusion could be drawn as only one participant reported results found with an ODR. 4.2 PERFORMANCE EVALUATION FOR THE GROUP OF LABORATORIES A comparison has been made between the reproducibilities R target as declared by the relevant standard method (e.g. ISO or ASTM) and the reproducibilities as found for the group of participating laboratories (= 2.8*sd). For all tests evaluated, the number of significant results, the average results, the calculated reproducibilities (2.8 * sd) and the target reproducibilities R target, derived from ISO or ASTM are compared in the next 3 tables. Parameter unit n average 2.8 * sd R (target) Mooney Viscosity MML MU Mooney Viscosity UML MU table 4: reproducibilities of sample 529 (raw rubber) iis5p2 page 8 of 32

9 Parameter unit n average 2.8 * sd R (target) Tensile Strength MPa Modulus 1% Mpa Modulus 2% MPa Unknown Modulus 3% MPa Unknown Elongation at Break % Tear Test kn/m Hardness table 5: reproducibilities of sample 53 (pre-cured material) o Parameter unit n average 2.8 * sd R (target) Abrasion Test, rel. vol.loss mm Density Mg/m unknown Hardness o Tensile Strength MPa Modulus 1% MPa Modulus 2% MPa unknown Modulus 3% MPa unknown Elongation at Break % MDR Ml dn.m MDR Mh dn.m MDR Ts1 min MDR Ts2 min unknown MDR Tc1 min unknown MDR Tc25 min unknown MDR Tc5 min MDR Tc9 min MDR Tc95 min unknown table 6: reproducibilities of sample 531 (cured by participants) Without further statistical calculations it can be concluded that for some determinations there is a reasonable compliance of the group of participating laboratories with the relevant standards. The problematic tests have been discussed in paragraph COMPARISON OF THE PROFICIENCY TEST OF MAY 25 WITH PREVIOUS PT S May 25 May 24 May 23 May 22 May 21 Number of reporting labs Number of Results reported Statistical outliers Percentage outliers 4.9% 4.1% 3.6% 4.9% <1% table 7: comparison with previous proficiency tests. In proficiency tests, outlier percentages of 3% - 7.5% are quite normal. iis5p2 page 9 of 32

10 The performance of the determinations of the proficiency tests was compared against the requirements of the respective standards. The conclusions are given the following table: Determination May 25 May 24 May 23 May 22 May 21 Mooney Viscosity MML Mooney Viscosity UML Tensile Strength /- Modulus 1% Elongation at Break -- +/ Tear Test -- +/ Hardness +/- +/ Abrasion Test, rel. vol.loss Hardness Tensile Strength +/ Modulus 1% Elongation at Break MDR Ml +/ n.e. MDR Mh n.e. MDR Ts n.e. MDR Tc n.e. MDR Tc9 ++ +/ n.e. table 8: comparison determinations against the standard The performance of the determinations against the requirements of the respective standards is listed in the above table. The following performance categories were used: ++: group performed much better than the standard + : group performed better than the standard +/-: group performance equals the standard - : group performed worse than the standard -- : group performed much worse than the standard n.e: not evaluated 5 DISCUSSION Evaluations of the results show that for some determinations a significant improvement is visible, while for other determinations the performance got worse. Every year new participants joined the proficiency test scheme, while others stopped participation; this makes comparison of this round with former rounds in order to evaluate any quality progress rather difficult. By the results found on the compound it was confirmed that the spreads were higher for the participant cured sample than for the pre-cured sample. This effect is most visible for the parameters: Tensile strength, Modulus 1%, 2% and 3%. This is probably caused due the high sensitivity for small parameter changing during sample treatment procedure prior to, during and after the vulcanisation step. iis5p2 page 1 of 32

11 APPENDIX 1 Determination of Mooney Viscosity MML(1+4)1 o C on sample 529; results in MU lab method value mark z-score remarks ISO ISO ISO ISO ISO D ISO G(.1) ISO normality OK n 7 outliers 1 mean (n) 5.53 st.dev. (n).559 R(calc.) 1.56 RSD R (calc) = 1.1 % R(ISO289:94) 5.86 RSD R (ISO289:94) = 4.1 % Kernel Density iis5p2 page 11 of 32

12 Determination of Mooney Viscosity UML(1+4)1 o C on sample 529; results in MU lab method value mark z-score remarks ISO ISO ISO ISO ISO D ISO G(.1) ISO normality not OK n 7 outliers 1 mean (n) 5.21 st.dev. (n).615 R(calc.) 1.72 RSD R (calc) = 1.2 % R(ISO289:94) 3.18 RSD R (ISO289:94) = 2.3 % Kernel Density iis5p2 page 12 of 32

13 Determination of Tensile strength on pre-cured sample 53; results in MPa lab method value mark z-score remarks 1113 ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO G(.5) D ISO ISO normality OK n 17 outliers 1 mean (n) st.dev. (n) R(calc.) 5.51 RSD R (calc) = 7.1 % R(D412:2) RSD R (D412:2) = 7.5 % Kernel Density iis5p2 page 13 of 32

14 Determination of Modulus 1% on pre-cured sample 53; results in MPa lab method value mark z-score remarks ISO G(.5) ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO D ISO ISO normality not OK n 15 outliers 1 mean (n) st.dev. (n).123 R(calc.).345 RSD R (calc) = 6.3 % R(D412:2).776 RSD R (D412:2) = 14.2 % Kernel Density iis5p2 page 14 of 32

15 Determination of Modulus 2% on pre-cured sample 53; results in MPa lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO D ISO ISO normality OK n 17 outliers mean (n) st.dev. (n).3763 R(calc.) 1.54 RSD R (calc) = 8.1 % R(lit.) Unknown RSD R (iis24) = 1. % Kernel Density iis5p2 page 15 of 32

16 Determination of Modulus 3% on pre-cured sample 53; results in MPa lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO D ISO ISO normality OK n 17 outliers mean (n) st.dev. (n).7172 R(calc.) 2.8 RSD R (calc) = 8.1 % R(lit.) unknown RSD R (iis24) = 7.4 % Kernel Density iis5p2 page 16 of 32

17 Determination of Elongation at Break on pre-cured sample 53; results in % lab method value mark z-score remarks 1113 ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO ISO D ISO ISO normality OK n 18 outliers mean (n) st.dev. (n) R(calc.) RSD R (calc) = 5.3 % R(D412:2) 6.12 RSD R (D412:2) = 3.5 % Kernel Density iis5p2 page 17 of 32

18 Determination of Tear Test on pre-cured sample 53; results in kn/m lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO C ISO ISO normality OK n 8 outliers mean (n) st.dev. (n) R(calc.) RSD R (calc) = 42.8 % R(ISO34:94) 29.4 RSD R (ISO34:94) = 21.1 % Kernel Density iis5p2 page 18 of 32

19 Determination of Hardness on pre-cured sample 53; results in o lab method value mark z-score remarks 1113 ISO ISO48 54 G(.1) ISO ISO ISO ISO ISO ISO ISO ISO ISO D224 6/SHORE A ISO normality not OK n 11 outliers 1 mean (n) st.dev. (n) R(calc.) 4.44 RSD R (calc) = 2.7 % R(ISO48:94) 4.47 RSD R (ISO48:94) = 2.7 % Kernel Density iis5p2 page 19 of 32

20 Determination of Abrasion test, relative volume loss on participant cured sample 531; results in mm 3 lab method value mark z-score remarks ISO ISO ISO ISO ISO G(.1) ISO normality OK n 5 outliers 1 mean (n) st.dev. (n) 1.22 R(calc.) RSD R (calc) = 7.6 % R(DRAFTISO4649) 1. RSD R (ISO4649) = 2.7 % iis5p2 page 2 of 32

21 Determination of Density on participant cured sample 531; results in Mg/m 3 lab method value mark z-score remarks ISO ISO ISO ISO ISO G(.5) ISO ISO normality OK n 6 outliers 1 mean (n) st.dev. (n).217 R(calc.).61 RSD R (calc) =.2 % R(lit) unknown RSD R (iis24) =.4 % iis5p2 page 21 of 32

22 Determination of Hardness on participant cured sample 531; results in o lab method value mark z-score remarks ISO48 59 C -.5 First reported 57 ISP ISO ISO ISO ISO D ISO ISO normality not OK n 9 outliers mean (n) 59.8 st.dev. (n) 1.99 R(calc.) 3.8 RSD R (calc) = 1.8 % R(ISO48:94) 4.47 RSD R (ISO48:94) = 2.7 % Kernel Density iis5p2 page 22 of 32

23 Determination of Tensile Strength on participant cured sample 531; results in MPa lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO ISO ISO D ISO G(.5) ISO ISO normality OK n 11 outliers 1 mean (n) st.dev. (n) 1.78 R(calc.) RSD R (calc) = 7.5 % R(D412:2) 4.95 RSD R (D412:2) = 7.4 % Kernel Density iis5p2 page 23 of 32

24 Determination of Modulus 1% on participant cured sample 531; results in MPa lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO ISO D G(.5) ISO ISO ISO normality OK n 1 outliers 1 mean (n) 2.43 st.dev. (n).1964 R(calc.).55 RSD R (calc) = 9.6 % R(D412:2).641 RSD R (D412:2) = 11.2 % Kernel Density iis5p2 page 24 of 32

25 Determination of Modulus 2% on participant cured sample 531; results in MPa lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO ISO ISO D ISO ISO ISO normality OK n 12 outliers mean (n) 5.38 st.dev. (n).5624 R(calc.) RSD R (calc) = 11.2 % R(lit) unknown RSD R (iis24) = 14.2 % Kernel Density iis5p2 page 25 of 32

26 Determination of Modulus 3% on participant cured sample 531; results in MPa lab method value mark z-score remarks ISO ISO ISO ISO ISO ISO ISO ISO D ISO ISO ISO normality OK n 12 outliers mean (n) st.dev. (n).9 R(calc.) 2.52 RSD R (calc) = 9.4 % R(lit) unknown RSD R (iis24) = 11.2 % Kernel Density iis5p2 page 26 of 32

27 Determination of Elongation at Break on participant cured sample 531; results in % lab method value mark z-score Remarks ISO ISO ISO ISO ISO DG(.5) ISO G(.1) ISO ISO ISO ISO ISO ISO DG(.5) -2.4 normality OK n 9 outliers 3 mean (n) st.dev. (n) R(calc.) RSD R (calc) = 5.8 % R(D412:2) 55.7 RSD R (D412:2) = 3.6 % Kernel Density iis5p2 page 27 of 32

28 Determination of Vulcanisation Characteristics (MDR) on participant cured sample 531 lab method Ml (dnm) Mh (dnm) Ts1 (min) Ts2 (min) Tc1 (min) Tc25 (min) Tc5 (min) Tc9 (min) Tc95 (min) ISO ISO ISO ISO ISO652 *) ISO ISO D ISO normality OK OK Not OK OK OK OK OK OK OK n outliers mean (n) st.dev. (n) R(calc.) R(D5289:1) unknown unknown unknown unknown RSD R (calc) 4.7 % 8.1 % 3.2 % 3.5 % 3.9 % 3.3 % 4.6 % 1.6 % 2. % RSD R (D5289:1) 4.4 % 4.2 % 2.2 % (5. %) (6. %) (1.6 %) 2.1 % 2.1 % (2.7 %) *) results found with Goettfert Elastograph **) results between brackets are results found in the round robin of 24 ***) results in Italic are statistical outliers via Grubbs lab method Z (targ) Ml Z (targ) Mh Z (targ) Ts1 Z (targ) Ts2 Z (targ) Tc1 Z (targ) Tc25 Z (targ) Tc5 Z (targ) Tc9 Z (targ) Tc iis5p2 page 28 of 32

29 Ml (dn.m) for MDR Vulcanisation Characteristics Mh (dn.m) for MDR Vulcanisation Characteristics Ts1 (min) for MDR Vulcanisation Characteristics Tc5 (min) for MDR Vulcanisation Characteristics Tc9 (min) for MDR Vulcanisation Characteristics iis5p2 page 29 of 32

30 Determination of Vulcanisation Characteristics (ODR) on participant cured sample 531 lab method Ml (dnm) Mh (dnm) Ts1 (min) Ts2 (min) Tc1 (min) Tc25 (min) Tc5 (min) Tc9 (min) Tc95 (min) ISO iis5p2 page 3 of 32

31 APPENDIX 2 List of number of participants per country Number of laboratories Country 2 labs in BELGIUM 2 labs in FRANCE 4 labs in GERMANY 1 lab in INDIA 1 lab in KOREA 1 lab in ROMANIA 1 lab in RUSSIA 2 labs in SPAIN 1 lab in SWEDEN 1 lab in THAILAND 2 labs in THE NETHERLANDS 1 lab in U.S.A. 1 lab in VIETNAM iis5p2 page 31 of 32

32 APPENDIX 3 Abbreviations: C D(.1) D(.5) G(.1) G(.5) DG(.1) DG(.5) = final result after checking of first reported suspect result = outlier in Dixon s outlier test = straggler in Dixon s outlier test = outlier in Grubbs outlier test = straggler in Grubbs outlier test = outlier in Double Grubbs outlier test = straggler in Double Grubbs outlier test Literature: 1 i.i.s. Interlaboratory Studies, Protocol for the Organisation, Statistics & Evaluation, November 23 2 ISO ISO 5725, parts 1-6, M. Thompson and R. Wood, J. AOAC Int, 76, 926, (1993) 5 W.J. Youden and E.H. Steiner, Statistical Manual of the AOAC, (1975) 6 IP 367/84 7 DIN 3842 T41/42 8 P.L. Davies, Fr. Z. Anal. Chem, 331, 513, (1988) 9 J.N. Miller, Analyst, 118, 455, (1993) 1 ISO 9936:97 11 Analytical Methods Committee Technical brief, No4 January The Royal Society of Chemistry 22, Analyst 22, 127 page , P.J. Lowthian and M. Thompson (see iis5p2 page 32 of 32