AATCC 61-2007 耐洗色牢度

Developed in 1950 by AATCC Committee RA60; revised 1952, 1954, 1957, 1960, 1961, 1970, 1972, 1986 (title change), 1989, 1993, 1994, 1996, 2003, 2006 (title change), 2007; reaffirmed 1956, 1962, 1965, 1968, 1969, 1975, 1980, 1985; editorially revised 1973, 1974, 1975, 1976, 1981, 1983, 1984, 1991, 1995, 1998, 2002, 2004; editorially re-vised and reaffirmed 2001. Partly equivalent to ISO 105-C06.1.Purpose and Scope1.1These accelerated laundering tests are to evaluate the colorfastness to laun-dering of textiles which are expected to withstand frequent laundering. The fabric color loss and surface changes resulting from detergent solution and abrasive ac-tion of five typical hand or home launder-ings, with or without chlorine, are roughly approximated by one 45 min test (see 9.2-9.6). However, the staining ef-fect produced by five typical hand or home launderings cannot always be pre-dicted by the 45min test. Staining is a function of the ratio of colored to undyed fabrics, fiber content of fabrics in the wash load and other end-use conditions which are not always predictable.1.2 When this test method was origi-nally developed, various options of this method were intended to evaluate the color change and staining by five home or commercial launderings, on an accel-erated basis. Throughout the years, com-mercial laundering procedures have changed and commercial cleaning today involves many different types of pro-cesses, dependent on the type of product being cleaned that cannot be duplicated by one accelerated laboratory procedure. In 2005, all references to commercial laundering were removed as it is not known if these procedures accurately rep-licate typical commercial laundering pro-cesses used today.2. Principle2.1Specimens are tested under appro-priate conditions of temperature, deter-gent solution, bleaching and abrasive ac-tion such that the color change is similar to that occurring in five hand or home launderings. The color change is obtained in a conveniently short time. The abra-sive action is a result of the frictional ef-fects of fabric against canister, the low li-quor ratio and the impact of the steel balls on the fabric.3. Terminology3.1colorfastness, n.—the resistance ofa material to change in any of its colorcharacteristics, to transfer of its color-ant(s) to adjacent materials or both, as aresult of the exposure of the material toany environment that might be encoun-tered during the processing, testing, stor-age or use of the material.3.2laundering, n.—of textile mate-rials, a process intended to remove soilsand/or stains by treatment (washing) withan aqueous detergent solution and nor-mally including subsequent rinsing, ex-tracting and drying.4. Safety PrecautionsNOTE: These safety precautions arefor information purposes only. The pre-cautions are ancillary to the testing proce-dures and are not intended to be all inclu-sive. It is the user’s responsibility to usesafe and proper techniques in handlingmaterials in the test method. Manufactur-ers MUST be consulted for specific de-tails such as material safety data sheetsand other manufacturer’s recommenda-tions. All OSHA standards and rulesmust also be consulted and followed.4.1Good laboratory practices shouldbe followed. Wear safety glasses in alllaboratory areas.4.2All chemicals should be handledwith care.4.3The 1993 AATCC Standard Refer-ence Detergent WOB may cause irrita-tion. Care should be taken to prevent ex-posure to skin and eyes.4.4An eyewash/safety shower shouldbe located nearby for emergency use.4.5Manufacturer’s safety recommen-dations should be followed when operat-ing laboratory testing equipment.5. Apparatus, Reagents and Materials5.1Launder-Ometer or other compara-ble equipment (see 12.1).5.1.1A laundering machine for rotat-ing closed canisters in a thermostaticallycontrolled water bath at 40 ± 2 rpm (see12.1).5.1.2Stainless steel lever lock canis-ters Type 1 (see 12.1) 500 mL (1 pt), 75 ×125 mm (3.0 × 5.0 in.) for Test No. 1A.5.1.3Stainless steel lever lock canis-ters Type 2 (see 12.1) 1200 mL, 90 × 200mm (3.5 × 8.0 in.) for Tests No. 2A, 3A,4A and 5A.5.1.4Adapter plates for holding canis-ters (see 5.1.3) on laundering machineshaft (see 12.1).5.1.5Stainless steel balls, 6 mm (0.25in.) in diameter (see 12.1).5.1.6Teflon fluorocarbon gaskets (see7.4.2, 12.1 and 12.2).5.1.7Preheater/storage module (see7.4, 12.1 and 12.3).5.2Scales for rating test results.5.2.1AA TCC Chromatic TransferenceScale (see 12.4).5.2.2Gray Scale for Color Change (see12.4).5.2.3Gray Scale for Staining (see12.4).5.3Reagents and materials.5.3.1Multifiber test fabrics No. 1 andFB (8 mm [0.33 in.] bands) containsbands of acetate, cotton, nylon, silk, vis-cose rayon and wool. Multifiber test fab-rics No. 10, and FA (8 mm [0.33 in.]bands) and No. 10A and FAA (15 mm[0.6 in.] bands) contain bands of acetate,cotton, nylon, polyester, acrylic and wool(see 12.5).5.3.2 Bleached cotton test fabric, 32 ×32 ends × picks/cm (80 × 80 ends ×picks/in.) construction, 100 ± 3 g/m2 (3.0± 0.1 oz/yd2), desized without fluorescentwhitening agent (see 12.5).5.3.31993 AATCC Standard Refer-ence Detergent WOB (without fluores-cent whitening agent and without phos-phate) (see 10.5 and 12.6).5.3.41993 AATCC Standard Refer-ence Detergent (with fluorescent whiten-ing agent) (see 10.5 and 12.6).5.3.5Water, distilled or deionized (see12.7).5.3.6Sodium hypochlorite (NaOCl)bleach (see 12.8).5.3.7Sodium carbonate (Na2CO3).5.3.8Sulfuric acid (H2SO4), 10% (see12.8.1).5.3.9Potassium iodide (KI), 10% (see12.8.1).5.3.10Sodium thiosulfate (Na2S2O3),0.1N (see 12.8.1).5.3.11Crockmeter test cloth cut in 50mm (2 in.) squares (see 12.9).5.3.12White cards (specimen mounts)with Y tristimulus value at least 85%.6. Test Specimens6.1The sizes of the specimens requiredfor the various tests are as follows:50 × 100 mm (2.0 × 4.0 in.) for TestNo. 1A,50 × 150 mm (2.0 × 6.0 in.) for TestsNo. 2A, 3A, 4A and 5A.6.2Test only one specimen in eachcanister.6.2.1Test one specimen per laboratorysample. Replication may be advisable forAATCC Test Method 61-2007Colorfastness to Laundering: Acceleratedimproved precision.6.3To determine staining in Tests No. 1A and 2A, use multifiber test fabric. To determine staining in Test No. 3A, use ei-ther multifiber test fabric or bleached cot-ton test fabric. With respect to Test No. 3A, the use of multifiber test fabric is optional but the staining of acetate, nylon, polyester and acrylic is disregarded unless one of these fibers is present in the fabric being tested or known to be in the final garment. For Test 3A, multifiber test fabric with heat-sealed edges is recommended. Stain-ing is not determined in Tests No. 4A and 5A (see 12.10 and 12.11).6.4Specimen preparation.6.4.1Preparation with multifiber test fabric with individual component bands 8mm (0.33 in.) wide or with bleached cotton test fabric. Prepare pieces with a 50 mm (2.0 in.) square of multifiber test fabric cloth or bleached cotton test fabric (as required) sewn, stapled or suitably attached along one 50 mm (2.0 in.) edge of the test specimen and in contact with the face of the material. When multifiber test fabric is used, attach it so that each of the six fiber bands is along the 50 mm (2.0in.) edge of the specimen with the wool on the right. The fiber bands in the multifiber test fabric will be parallel to the lengthwise direction of the test specimen.6.4.2Preparation with multifiber test fabric with individual component bands15 mm (0.6 in.) wide. Prepare pieces witha 50 × 100 mm (2.0 × 4.0 in.) rectangle of multifiber test fabric sewn, stapled or suitably attached centered along one 100 mm (4.0 in.) or 150 mm (6.0 in.) edge of the test specimen and in contact with the face of the material. Attach it so that each of the six fiber bands will be parallel to the widthwise direction of the specimen. Attach and secure the wool band at the top of the specimen to avoid fiber loss. 6.4.3It is recommended that knitted fabrics be sewn or stapled at the four edges to equivalent size pieces of bleached cotton test fabric to avoid rolled edges and to assist in obtaining a uniform test result over the entire surface. Attach the multifiber test fabric to the face of the knitted fabric.6.4.4For pile fabric specimens with a pile lay direction, attach the multifiber test fabric at the top of the specimen with the pile lay direction pointing away from the top of the specimen.6.5When the textile to be tested is yarn, specimens may be tested using Op-tion 1 or Option 2.6.5.1Option 1. Knit yarn on an appro-priate sample knitting machine. Prepare specimens and multifiber test fabrics ac-cording to 6.1-6.4.3. Keep one knitted specimen of each sample as an unwashed original.6.5.2Option 2. Prepare two 110 m (120 yd) skeins of each yarn. Fold the skein so that there is a uniform amount ofyarn across a 50 mm (2 in.) width with alength appropriate for the procedure to beused. Keep one skein of each sample asan unwashed original. Sew or stapleCrockmeter test cloth squares (see 12.9)or squares of bleached cotton test fabrichaving approximately the same weightfolded over each end of the layered yarnspecimen. Attach a multifiber test fabricaccording to 6.4.1 or 6.4.2.7. Procedure7.1Table I summarizes the conditionsof the tests.7.2Adjust the laundering machine tomaintain the designated bath tempera-ture. Prepare the required volume ofwash liquor. Preheat this solution to theprescribed temperature.7.3Run Test No. 1A in 75 × 125 mm(3.0 × 5.0 in.) lever lock stainless steelcanisters. Run Tests No. 2A, 3A, 4A and5A in 90 × 200 mm (3.5 × 8.0 in.) leverlock stainless steel canisters.7.3.1For Tests No. 1A, 2A and 3A,add to the canister the amount of deter-gent solution designated in Table I.7.3.2For Test No. 4A, prepare a 1500ppm available chlorine solution. For 1 L,determine the amount of stock sodiumhypochlorite bleach solution (see 12.8) todilute as follows:159.4/% NaOCl = g to addWeigh the correct amount of bleach intoa volumetric flask and dilute to 1 L. Toeach canister, add 5 mL of 1500 ppmavailable chlorine solution and 45 mL ofdetergent solution making a total volumeof 50 mL.7.3.3For Test No. 5A, determine theamount of stock sodium hypochloritebleach solution (see 12.8) to dilute asfollows:4.54/% NaOCl = g to addWeigh the correct amount of bleach intoa graduated cylinder and add detergentsolution to make a total volume of 150mL. Prepare this solution separately foreach canister.7.3.4For all the tests, add the desig-nated number of stainless steel balls toeach canister.7.4The two options for preheating thecanisters to the test temperature are byuse of the laundering machine or the pre-heater/storage unit. If the canisters are tobe preheated in the laundering machine,proceed to 7.4.2.7.4.1Place the canisters in the pre-heater module at the prescribed test tem-perature. They are to remain in themodule for at least 2 min. Enter a wellcrumpled test specimen into each canister.7.4.2Clamp the covers on the canis-ters. A Teflon fluorocarbon gasket (see5.1.6) may be inserted between the neo-prene gasket and the top of each canisterto prevent contamination of the wash so-lution by the neoprene. Fasten the 75 ×125 mm (3.0 × 5.0 in.) lever lock canis-ters vertically and the 90 × 200 mm (3.5× 8.0 in.) lever lock canisters horizontallyin the adapters on the rotor of the laun-dering machine in such a manner thatwhen the canisters rotate, the coversstrike the water first. Place an equal num-ber of canisters on each side of the shaft.For canisters preheated in the module,proceed to 7.7.7.5Start the rotor and run it for at least2 min to preheat the canisters.7.6Stop the rotor and with a row ofcanisters in an upright position, unclampthe cover of one canister, enter a wellcrumpled test specimen into the solutionand replace the cover, but do not clamp it.Repeat this operation until all the canis-ters in the row have been loaded. Thenclamp the covers in the same order inwhich the canisters were loaded (delayclamping the covers to allow equalizationof pressure). Repeat this operation untilall rows of canisters have been loaded.7.7Start the laundering machine andrun it at 40 ± 2 rpm for 45 min.7.8The rinsing, extracting and dryingprocedures are the same for all the tests.Stop the machine, remove the canistersand empty the contents into beakers,keeping each test specimen in a separatebeaker. Rinse each test specimen threetimes, in beakers, in distilled or deionizedwater at 40 ± 3°C (105 ± 5°F) for 1 minperiods with occasional stirring or handsqueezing. To remove excess water, cen-trifuge, blot or pass the test specimensthrough wringer rolls. Dry the specimensin an air circulating oven in which theTable I—Test Conditions aTestNo.Temp TotalLiquorVolumePercentDetergentof TotalVolumeAvailableChlorineof TotalVolumeNo.SteelBalls Time °C (±°2)°F(±°4)1A40105200 mL0.37%None1045 Min 2A491201500.15None5045 3A71160500.15None10045 4A71160500.150.015%10045 5A491201500.150.0275045a Refer to Section 9 for objectives for each test method.temperature does not exceed 71°C (160°F), or tumble dry in a nylon mesh bag in an automatic tumble dryer at nor-mal cycle, which has an exhaust tempera-ture of 60-71°C (140-160°F), or air dry.7.9 Allow specimens to condition at 65± 2% relative humidity and 21 ± 1°C (70± 2°F) for 1 h before evaluating.7.10Prepare tested fabric specimens and adjacent fabrics for evaluation by trimming off raveled yarns and lightly brushing off any loose fiber and yarn on the fabric surfaces. Brush pile fabric specimens in required direction to restore them as nearly as possible to the same pile angle as the untreated specimens. Specimens should be smoothed or flat-tened if they are wrinkled and messy due to washing and/or drying. Specimens may be mounted on cards to facilitate identification and handling in their evalu-ation. For consistency in backing mate-rial, use a white mounting card with Y tristimulus value of at least 85%. Mount-ing material must not be visible in the area to be viewed and must not interfere with rating as specified in 5.1 of both AATCC Evaluation Procedures 1 and 2 for the Gray Scale for Color Change and Gray Scale for Staining or instrumental assessment of color according to AATCC Evaluation Procedure 7, Instrumental As-sessment of the Change in Color of a Test Specimen.7.10.1Yarn skein specimens should be combed and brushed for improved align-ment of the yarns before comparison with the unwashed original. The original spec-imens may also need further combing and brushing for uniformity of appearance.8. Evaluation8.1Evaluation of color change.8.1.1Evaluate the color change of the test specimens as directed in AATCC Evaluation Procedure 1 using the Gray Scale for Color Change. For improved precision and accuracy the specimens should be rated by more than one rater. Grade 5—negligible or no change as shown in Gray Scale Step 5.Grade 4.5—change in color equivalent to Gray Scale Step 4.5.Grade 4—change in color equivalent to Gray Scale Step 4.Grade 3.5—a change in color equiva-lent to Gray Scale Step 3.5.Grade 3—change in color equivalent to Gray Scale Step 3.Grade 2.5—change in color equivalent to Gray Scale Step 2.5.Grade 2—change in color equivalent to Gray Scale Step 2.Grade 1.5—change in color equivalent to Gray Scale Step 1.5.Grade 1—change in color equivalent to Gray Scale Step 1.8.1.2The color change can be quanti-tatively determined by measuring thecolor difference between the unwashedsample and a test specimen using a suit-able colorimeter or spectrophotometerwith the appropriate software (seeAATCC Evaluation Procedure 7, Instru-mental Assessment of the Change inColor of a Test Specimen).8.2Evaluation of staining.8.2.1Evaluate staining (see 12.10) asdirected in AA TCC Evaluation Procedure2 using the Gray Scale for Staining or asdirected in AA TCC Evaluation Procedure8 using the Chromatic TransferenceScale. The scale used should be indicatedwhen reporting the test results.Grade 5—negligible or no color transfer.Grade 4.5—color transfer equivalent toStep 4-5 on the Gray Scale for Staining orRow 4.5 on the 9-step AA TCC Chro-matic Transference Scale.Grade 4—color transfer equivalent toStep 4 on the Gray Scale for Staining orRow 4 on the 9-step AATCC ChromaticTransference Scale.Grade 3.5—color transfer equivalent toStep 3-4 on the Gray Scale for Staining orRow 3.5 on the 9-step AA TCC Chro-matic Transference Scale.Grade 3—color transfer equivalent toStep 3 on the Gray Scale for Staining orRow 3 on the 9-step AATCC ChromaticTransference Scale.Grade 2.5—color transfer equivalent toStep 2-3 on the Gray Scale for Staining orRow 2.5 on the 9-step AA TCC Chro-matic Transference Scale.Grade 2—color transfer equivalent toStep 2 on the Gray Scale for Staining orRow 2 on the 9-step AATCC ChromaticTransference Scale.Grade 1.5—color transfer equivalent toStep 1-2 on the Gray Scale for Staining orRow 1.5 on the 9-step AA TCC Chro-matic Transference Scale.Grade 1—color transfer equivalent toStep 1 on the Gray Scale for Staining orRow 1 on the 9-step AATCC ChromaticTransference Scale.8.2.2The color transferred to the mul-tifiber test fabric or bleached cotton testfabric square of 6.4.1 can be quantita-tively determined by measuring the colordifference between a piece of the originalmaterial and the stained material. Multifi-ber test fabrics No. 10A or FAA havebands of sufficient width to be within theaperture diameter capability of many col-orimeters and spectrophotometers (seeAATCC Evaluation Procedure 6, Instru-mental Color Measurement and 12.14).9. Interpretation of Results9.1Results from these tests are in-tended to approximate the color changeeffects (see 1.1) of five typical homelaunderings. These are accelerated tests,and in obtaining the required degree ofacceleration some of the conditions, suchas temperature, were purposely exagger-ated. The tests have remained largely thesame over many years while laundry de-tergents, washers and dryers, laundrypractices and fabrics have changed (seeAATCC monograph “Standardization ofHome Laundry Test Conditions,” else-where in this T ECHNICAL M ANUAL).Consequently, caution in interpreting testresults is advisable.9.2Test No. 1A—This test is for eval-uating the colorfastness of textiles thatare expected to withstand repeated handlaundering at low temperature. Speci-mens subjected to this test should showcolor change similar to that produced byfive typical careful hand launderings at atemperature of 40 ± 3°C (105 ± 5°F).9.3Test No. 2A—This test is for eval-uating the colorfastness to washing oftextiles that are expected to withstand re-peated low temperature machine launder-ing in the home. Specimens subjected tothis test should show color change similarto that produced by five home machinelaunderings at medium or warm setting inthe temperature range of 38 ± 3°C (100 ±5°F).9.4Test No. 3A—This test is for eval-uating colorfastness to washing of tex-tiles considered washable under vigorousconditions. Specimens subjected to thistest should show color change similar tothat produced by five home machinelaunderings at 60 ± 3°C (140 ± 5°F),without chlorine.9.5 Test No. 4A—This test is for evalu-ating the colorfastness to washing of tex-tiles laundered in the presence of avail-able chlorine. Specimens subjected tothis test should show color change similarto that produced by five home machinelaunderings at 63 ± 3°C (145 ± 5°F) with3.74 g per L (0.50 oz/gal) of 5% availablechlorine per 3.6 kg (8.0 lb) load.9.6 Test No. 5A—This test is for eval-uating the colorfastness to washing oftextiles that may be laundered in the pres-ence of available chlorine. Specimenssubjected to this test should show colorchange similar to that produced by fivehome machine launderings at 49 ± 3°C(120 ± 5°F) with 200 ± 1 ppm availablechlorine.10. Report10.1Report the test number.10.2Report the grade number deter-mined for color change in 8.1 and thestaining grade numbers for the evaluatedfibers in the multifiber test fabric and/orbleached cotton test fabric as determinedin 8.2.10.3State which scale (Gray Scale forStaining or AATCC Chromatic Transfer-ence Scale) was used in evaluating stain-ing (see 12.12).10.4Report the multifiber test fabric used and if bleached cotton test fabric was employed to avoid knit curling. 10.5Report the detergent used with color change and staining results (see 12.6).10.6Report which laundering ma-chine is used.11. Precision and Bias11.1Precision and bias statements have been developed for Tests No. 2A and 5A. Although correlation work has been done, no precision and bias state-ments have been developed for Tests No. 1A, 3A and 4A.11.1.1Because of changes in the deter-gents used in this method, these precision and bias statements may not apply to data or information obtained with the cur-rently available detergents.11.2Test No. 2A.11.2.1Summary. An interlaboratory test was carried out in May 1985 to estab-lish the precision of Test No. 2A. A part of the test was to determine if the wider 15 mm (0.6 in.) No. 10A multifiber test fabric could be substituted for the 8 mm (0.33 in.) wide No. 10. The complete test consisted of six laboratories evaluating 10 materials in duplicate by one operator using Test No. 2A.11.2.2Color Change. Three raters from six laboratories independently eval-uated nine materials in duplicate using the Gray Scale for Color Change. The components of variance as standard devi-ations of the colorfastness grades (aver-ages of variances for No. 10 and No. 10A multifiber test fabrics) were calculated as follows:Single-OperatorComponent0.29Within-LaboratoryComponent0.29Between-LaboratoryComponent0.29 11.2.3Critical Differences. For the components of variance reported in 11.2.2, two averages of observed values should be considered significantly differ-ent at the 95% probability level if the dif-ference is equal to or exceeds the critical differences shown in Table II.Table II—Critical Differences, Grades,for the Condition Noted aNo. of ObservationsSingle-OperatorPrecisionWithin-LabPrecisionBetween-LabPrecision10.80 1.12 1.3730.460.92 1.2150.360.87 1.18a The critical differences were calculated using t=1.950 which is based on infinite degrees of freedom.11.2.4Staining. Three raters indepen-dently rated the six fibers of the multifi-ber test fabric (No. 10 and No. 10A) for10 materials at six laboratories using theGray Scale for Staining. Of the 60 possi-ble fiber/fabric combinations, only 51could be used. The components of vari-ance were averaged for the No. 10 andNo. 10A multifiber test fabrics and ap-pear below as standard deviations ofstaining ratings:Single OperatorComponent0.27Within-LaboratoryComponent0.34Between-LaboratoryComponent0.2511.2.5Critical Differences. For thecomponents of variance reported in11.2.4, two averages of observed valuesshould be considered significantly differ-ent at the 95% probability level if the dif-ference equals or exceeds the critical dif-ferences shown in Table III.11.2.6 Bias. Tests comparing fivehome launderings at 40°C (105°F) withone Launder-Ometer Test No. 2A indi-cate there is no bias between the twomethods for the colorfastness and stain-ing levels evaluated.11.3Test No. 5A, Chlorine Bleach.11.3.1Summary. An interlaboratorytest was carried out in 1984 to establishthe precision of Test No. 5A for deter-mining the effect of chlorine bleach onthe colorfastness of fabrics. All speci-mens were laundered in a Launder-Ometer by one operator. Color change inTest No. 5A was determined both visu-ally and instrumentally. Details of the sta-tistical analysis of the data can be foundin the report, Third Interlaboratory Studyof Proposed Launder-Ometer Test forColorfastness of Fabrics to Chlorine andNon-Chlorine Bleaches, October 21,1985, by J. W. Whitworth, Milliken Re-search Corp., Spartanburg, SC.11.3.2Visual Assessment. Four materi-als were tested at each of five laborato-ries. Three raters visually assessed thecolor change of four specimens. Thecomponents of variance as standard devi-ations of colorfastness grades were calcu-lated as follows:Table III—Critical Differences, Grades,for the Condition Noted aNo. ofObservationsSingle-OperatorPrecisionWithin-LabPrecisionBetween-LabPrecision10.75 1.20 1.3930.43 1.03 1.2550.33 1.00 1.22a The critical differences were calculated using t=1.950 which is based on infinite degrees of freedom.Single OperatorComponent0.38Within-LaboratoryComponent0.28Between-LaboratoryComponent0.2711.3.3Critical Differences. For thecomponents of variance in 11.3.2, twoaverages of observed values should beconsidered significantly different at the95% probability level if the differenceequals or exceeds the critical differencesshown in Table IV.11.3.4Instrumental Assessment. Colorchange as total color difference(CIELAB) was measured on a spectro-photometer or colorimeter using aper-tures ranging in size from 13-51 mm(0.5-2.0 in.) in diameter, illuminant D65/10° observer or illuminant C/2° observer.Six materials were tested at each of sixlaboratories. One operator in each labora-tory tested four specimens of each fabric.The components of variance for ∆E* ex-pressed as coefficients of variation werecalculated to be:Single-OperatorComponent 6.8%Between-LaboratoryComponent11.2%11.3.5Critical Differences. For thecomponents of variance reported in11.3.4, two averages of observed valuesshould be considered significantly differ-ent at the 95% probability level if the dif-ference equals or exceeds the critical dif-ferences shown in Table V.Table IV—Critical Differences, Grades,for the Condition Noted aNo. ofObservationsSingle-OperatorPrecisionWithin-LabPrecisionBetween-LabPrecision1 1.03 1.29 1.4930.590.98 1.2350.460.91 1.17a The critical differences were calculated using t=1.950 which is based on infinite degrees of freedom.Table V—Critical Differences, Percent ofGrand Average for the Conditions Noted a,bNo. ofObservations inEach AverageSingle-OperatorPrecisionBetween-LaboratoryPrecision118.736.2310.832.858.432.1a The critical differences were calculated using t=1.950 which is based on infinite degrees of freedom.b To convert the values of the critical differences tounits of measure, multiply the critical differences bythe average of the two specific sets of data beingcompared and then divide by 100.。