1、Designation: D 2525 90 (Reapproved 2001)Standard Practice forSampling Wool for Moisture1This standard is issued under the fixed designation D 2525; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the design of a sampling plan to beused to obtain samples for the determination of the moisturecontent of grease wool,
3、scoured wool, carded wool, garnettedwool, wool top and intermediate products, and rovings.1.2 Directions are given for the designation of samplingunits, calculation of the number of sampling units required toachieve a preselected precision and confidence level or, alter-natively, for calculating the
4、 confidence limits for the meanbased on the variability of the sample tested.NOTE 1This practice for devising a sampling plan is intended for usein connection with Test Method D 1576 or Test Method D 2462. Thesampling of raw wool for the determination of clean wool fiber present iscovered in Practic
5、e D 1060.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Ref
6、erenced Documents2.1 ASTM Standards:D 123 Terminology Relating to Textiles2D 1060 Practice for Core Sampling of Raw Wool in Pack-ages for Determination of Percentage of Clean Wool FiberPresent2D 1576 Test Method for Moisture in Wool by Oven-Drying2D 2462 Test Method for Moisture in Wool by Distillat
7、ionwith Toluene2E 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a Lot or Process33. Terminology3.1 Definitions:3.1.1 laboratory sample, na portion of material taken torepresent the lot sample, or the original material, and u
8、sed inthe laboratory as a source of test specimens.3.1.2 lot, nin acceptance sampling, that part of a consign-ment or shipment consisting of material from one productionlot.3.1.3 lot sample, none or more shipping units taken atrandom to represent an acceptance sampling lot and used as asource of lab
9、oratory samples.3.1.4 sample, n(1) a portion of a lot of material which istaken for testing or record purposes.(2) the group of specimens used, or observations made,which provide information that can be used for makingstatistical inferences about the population from which theywere drawn.3.1.5 sampli
10、ng unit, nin wool, a portion of material that istaken at one time from one physical location and that iscombined with similar portions to make up the laboratorysample.3.1.5.1 DiscussionA sampling unit may or may not havethe same physical size as a specimen. Examples of samplingunits include: (1) for
11、 bulk materials seen as scoured wool, ahandful of wool conforming to a stated mass range, (2) forcored material, a minimum mass of material collected by oneinsertion of a coring tool, (3) for sliver, a stated length ofmaterial, and (4) a single package, such as a ball of top.3.1.6 specimen, na speci
12、fic portion of a material or alaboratory sample upon which a test is performed or which isselected for that purpose.3.1.7 For definitions of moisture, moisture content, moistureregain, and other textile terms used in this practice, refer toTerminology D 123.4. Summary of Practice4.1 Directions are g
13、iven for subdividing a lot of materialinto potential sampling units and for providing each potentialsampling unit with its own unique identification.4.2 Directions are given for calculating the number of suchsampling units required to give a preselected allowable varia-tion at a stated probability l
14、evel, or for calculating confidencelimits for the sample mean obtained for a given size of sample.4.3 Directions are given for deciding which particular sam-pling units should be chosen to constitute the required lotsample. These directions ensure that all potential samplingunits have approximately
15、the same chance of being selected forthe lot sample.1This practice is under the jurisdiction of the ASTM Committee D13 on Textiles,and is the direct responsibility of Subcommittee D13.13 on Wool and Wool Felt.Current edition approved Jan. 26, 1990. Published May 1990. Originallypublished as D 2525 6
16、6 T. Last previous edition D 2525 76 (1983).2Annual Book of ASTM Standards, Vol 07.01.3Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 This recommended practice furnishes directions for thesam
17、pling of wool of the various forms indicated in Section 1,in order that correct probability statements may be made aboutthe relationship between the sample mean and the populationmean. If these statements are to be correct, certain conditions,which are stated, must hold.5.2 This recommended practice
18、 requires that a deliberate actof randomization be performed so that all potential samplingunits have approximately the same chance of being taken andno sampling unit is deprived of its chance of being taken.5.3 In any case where insufficient information about thevariability of the sampling units wi
19、thin the lot is available,directions are given for calculating confidence limits for thesample mean so that a correct probability statement can still bemade.6. Preliminary Conditions6.1 If it is desired to calculate a sample size to achieve apreselected precision at a preselected level of confidence
20、,knowledge of the variation of the moisture content is neces-sary.6.1.1 The test method to be used must be the same methodthat was used to derive any prior information with respect tothe variability of the moisture content.6.1.2 The sampling unit must be the fundamental unit interms of which the var
21、iance is expressed. In other words, if thesampling unit is chosen to be a 25-g handful of bulk materialor a 4-yd (3.65-m) length of sliver, then the variance used mustbe the number that expresses the variability of these units, andthe number of sampling units which is calculated will be thenumber of
22、 such units required. The sampling unit is notnecessarily the same thing as a specimen.6.1.3 The lot designated for sampling must be statisticallyhomogeneous. This is equivalent to saying that the lot shall notbe composed of a mixture of two or more parts, the moisturecontent of which is distributed
23、 sufficiently differently that if themoisture content of the entire lot were measured, a plot of themoisture content versus the number of sampling units wouldshow a curve having more than one peak. (See Appendix X1.)If the test given in Appendix X1 leads to the conclusion that thelot cannot be consi
24、dered to be statistically homogeneous, thenit should be subdivided into groups that are homogeneous. Thepattern of runs found may indicate what the subgroups shouldbe.6.1.4 The magnitude of the variation of moisture contentwithin the homogeneous lot must be known. The magnitude ofthe variation is us
25、ually expressed as the standard deviation,although the range may also be used.6.2 If insufficient knowledge is available to ensure meetingthe above conditions, a sample of convenient size may beselected and confidence limits calculated for the mean usingthe information in the sample results. In this
26、 case, the onlycondition that applies is 6.1.3.7. Procedure7.1 Designate the form and size of the sampling unit,bearing in mind the conditions and precautions discussed inSections 5 and 6. Whenever possible, make the size of thesampling unit and specimen the same.7.1.1 The designation of the samplin
27、g unit depends on theform of the material and on the method to be used for makingmeasurements on the sample. The material to be sampled mayexist in one of three basic forms: bulk material such as scouredwool or picked blends of wools, packaged material such asbaled wool, or material put up in the fo
28、rm of packages withinpackages such as balls of top within cases or bales. The methodof measurement may require a specimen as large as a wholepackage of material, or as small as a few grams of material.7.1.2 Where the material to be sampled exists in some bulkform, such as scoured wool, or a blend th
29、at has been picked andstored in a bin, the designation of a sampling unit will dependupon the mechanics of drawing the sample. If hand sampling isthe method employed, the sampling unit will be a handful of acertain specified size. Whenever possible, the size of a sam-pling unit should be made to coi
30、ncide with the size of thespecimen required by the method of measurement because therandom variations observed in the test results are then directlyapplicable to the sampling units.7.1.3 When the material to be sampled exists in the form ofpackages such as baled wool or packages within packages,such
31、 as balls of wool top in cases or bales, the sampling unitcan be either an entire package or some portion of a package,depending upon the size of the specimen required.7.2 Identify each potential sampling unit in the lot bynumbering, coding, using geometrical coordinates, or by anyother systematic m
32、eans. It is important that by some means orother, all potential sampling units must be furnished with theirown unique identification so that none is deprived of its chanceof being sampled.7.2.1 In designing a sampling plan, it is necessary to devisea method for assigning to every potential sampling
33、unit in thelot a unique identification. This is a relatively simple task inthose instances where the sampling units are discrete packages,such as might be the case with balls of top if an entire ball isto be the sampling unit.7.2.2 With material in bulk form or with packaged materialin which the sam
34、pling unit is to be only a portion of thepackage, it is not as easy to identify uniquely each potentialsampling unit, and some method of approximating the idealsituation must be devised. See, for example, the instructionsgiven in Practice D 1060.7.2.3 For materials in loose bulk form, considerable i
35、nge-nuity and imagination may be required to effect a properidentification of the potential sampling units.7.3 Option 1This procedure is available for those in-stances where information is sufficient to enable the calculationof sample size required for a specified allowable variation andprobability
36、level.7.3.1 If the allowable variation and probability level are notstated in the applicable material specification or otherwiseestablished, determine for these factors values mutually agree-able to all parties interested in the test results.7.3.2 Whenever the material being tested has been produced
37、under statisically controlled conditions and records are avail-able, or information is available from prior tests on the samelot, estimate the universe standard deviation from these data.D 25252NOTE 2In many instances only an estimation of the variation likely tobe encountered in a lot is available,
38、 such as the limits beyond which valuesof moisture content are not likely to occur. Practice E 122 includesformulas for estimating the standard deviation for different distributionsbased on the extreme range of values expected. Whenever there is noinformation available as to the form of the distribu
39、tion, assuming arectangular distribution will yield a relatively conservative estimate.7.3.3 Based on values determined as directed in 7.3.1 and7.3.2, calculate the number of sampling units required, usingEq 1 or Table 1:n 5 t23 s2!/E2(1)where:n = number of sampling units required rounded to the nex
40、thigher whole number when the calculated value of n isequal to or less than 50 and rounded to the next highermultiple of five when the calculated value of n isgreater than 50,t = constant depending on the desired probability leveland equal to Students t for infinite degrees of freedomand two-sided l
41、imits, for example,Probability Level, % tt290 1.645 2.70695 1.960 3.84299 2.576 6.636s = standard deviation of individual observations, in unitsof the property being evaluated, andE = allowable variation of the test results expressed in unitsof the property being evaluated, which in some casesmay be
42、 a percentage.NOTE 3The arbitrarily chosen value for E refers to the allowablevariation in a test result based on observations still to be carried out underconditions of single-operator precision.7.3.4 Using a table of random numbers or any satisfactoryobjective randomizing procedure, decide which p
43、articular po-tential sampling units will make up the sample of the sizecalculated in 7.3.3.7.3.5 Acquire these particular sampling units by the methodrequired by the designation done in 7.1, using special care toavoid gain or loss of moisture by the sampling unit in theprocess of being taken. Weigh
44、these sampling units as rapidlyas possible as they are selected.7.4 Option 2This procedure is available for those in-stances where enough information to apply Option 1 is notobtainable or for those instances where all parties interested inthe results of the test agree to accept whatever precision ma
45、yresult from an agreed upon fixed sample size and probability inorder to reduce the cost of testing.7.4.1 Decide, by agreement between the parties interested inthe test results, on the number of sampling units to be taken andthe confidence level desired.7.4.2 Proceed as directed in 7.3.4 and 7.3.5.7
46、.4.3 After performing the tests, calculate the confidencelimits for the sample mean by Eq 2:Confidence limits 56ts/=n (2)where:n = number of sampling units in the sample,t = value of Students t for n 1 degrees of freedom,two-sided limits, and the specification probabilitylevel,4ands = sample standar
47、d deviation, defined by Eq 3:s 5 (ixi2 x!2/n 2 1!#1/2(3)NOTE 4The xiin the above equation are individual values for sam-pling units when the sampling unit and the specimen are the same size.When, however, more than one specimen is measured per sampling unit,the xiwill be averages of those specimens
48、belonging to a particularsampling unit. x is, of course, the grand average of all values.7.5 Having obtained a lot sample, there are alternative waysof acquiring specimens from it depending on the type ofinformation needed.7.5.1 Option 1 has been exercised and no information isneeded about variabili
49、ty:The entire lot sample is the laboratory sample. Condition thespecimen in accordance with Test Method D 1576.7.5.2 Option 1 has been exercised and information aboutvariability is wanted, or Option 2 has been exercised:Example 1: The sampling unit is greater than or equal to the4See, for instance, Hoel, P. G., Introduction to Mathematical Statistics, JohnWiley sampling; statistics; woolAPPENDIX(Nonmandatory Information)X1. SAMPLINGX1.1 Section 6.1.3 requires the assumption of statisticalhomogeneity in the lot being sampled, but in many cases it willnot be possib
