ASTM D2525-90(2008)
(Practice)Standard Practice for Sampling Wool for Moisture
Standard Practice for Sampling Wool for Moisture
SIGNIFICANCE AND USE
This recommended practice furnishes directions for the sampling of wool of the various forms indicated in Section 1, in order that correct probability statements may be made about the relationship between the sample mean and the population mean. If these statements are to be correct, certain conditions, which are stated, must hold.
This recommended practice requires that a deliberate act of randomization be performed so that all potential sampling units have approximately the same chance of being taken and no sampling unit is deprived of its chance of being taken.
In any case where insufficient information about the variability of the sampling units within the lot is available, directions are given for calculating confidence limits for the sample mean so that a correct probability statement can still be made.
SCOPE
1.1 This practice covers the design of a sampling plan to be used to obtain samples for the determination of the moisture content of grease wool, scoured wool, carded wool, garnetted wool, wool top and intermediate products, and rovings.
1.2 Directions are given for the designation of sampling units, calculation of the number of sampling units required to achieve a preselected precision and confidence level or, alternatively, for calculating the confidence limits for the mean based on the variability of the sample tested.
Note 1—This practice for devising a sampling plan is intended for use in connection with Test Method D 1576 or Test Method D 2462. The sampling of raw wool for the determination of clean wool fiber present is covered in Practice D 1060.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D2525 − 90 (Reapproved2008)
Standard Practice for
Sampling Wool for Moisture
This standard is issued under the fixed designation D2525; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 laboratory sample, n—a portion of material taken to
represent the lot sample, or the original material, and used in
1.1 This practice covers the design of a sampling plan to be
the laboratory as a source of test specimens.
used to obtain samples for the determination of the moisture
content of grease wool, scoured wool, carded wool, garnetted
3.1.2 lot, n—in acceptance sampling,thatpartofaconsign-
wool, wool top and intermediate products, and rovings. ment or shipment consisting of material from one production
lot.
1.2 Directions are given for the designation of sampling
units, calculation of the number of sampling units required to 3.1.3 lot sample, n—one or more shipping units taken at
achieve a preselected precision and confidence level or,
random to represent an acceptance sampling lot and used as a
alternatively,forcalculatingtheconfidencelimitsforthemean source of laboratory samples.
based on the variability of the sample tested.
3.1.4 sample, n—(1) a portion of a lot of material which is
taken for testing or record purposes.
NOTE 1—This practice for devising a sampling plan is intended for use
in connection with Test Method D1576 or Test Method D2462. The
(2) the group of specimens used, or observations made,
sampling of raw wool for the determination of clean wool fiber present is
which provide information that can be used for making
covered in Practice D1060.
statistical inferences about the population from which they
1.3 This standard does not purport to address all of the
were drawn.
safety concerns, if any, associated with its use. It is the
3.1.5 sampling unit, n— in wool, a portion of material that
responsibility of the user of this standard to establish appro-
is taken at one time from one physical location and that is
priate safety and health practices and determine the applica-
combined with similar portions to make up the laboratory
bility of regulatory limitations prior to use.
sample.
2. Referenced Documents
3.1.5.1 Discussion—A sampling unit may or may not have
the same physical size as a specimen. Examples of sampling
2.1 ASTM Standards:
units include: (1) for bulk materials seen as scoured wool, a
D123Terminology Relating to Textiles
handful of wool conforming to a stated mass range, (2) for
D1060PracticeforCoreSamplingofRawWoolinPackages
cored material, a minimum mass of material collected by one
for Determination of Percentage of Clean Wool Fiber
insertion of a coring tool, (3) for sliver, a stated length of
Present
material, and (4) a single package, such as a ball of top.
D1576Test Method for Moisture in Wool by Oven-Drying
D2462Test Method for Moisture in Wool by Distillation
3.1.6 specimen, n—a specific portion of a material or a
With Toluene
laboratory sample upon which a test is performed or which is
E122PracticeforCalculatingSampleSizetoEstimate,With
selected for that purpose.
Specified Precision, the Average for a Characteristic of a
3.1.7 Fordefinitionsofmoisture,moisturecontent,moisture
Lot or Process
regain, and other textile terms used in this practice, refer to
Terminology D123.
3. Terminology
3.1 Definitions:
4. Summary of Practice
1 4.1 Directions are given for subdividing a lot of material
This practice is under the jurisdiction of theASTM Committee D13 onTextiles
and is the direct responsibility of Subcommittee D13.13 on Wool and Felt.
into potential sampling units and for providing each potential
Current edition approved Aug. 1, 2008. Published October 2008. Originally
sampling unit with its own unique identification.
approved in 1966. Last previous edition approved in 2001 as D2525–90 (2001).
DOI: 10.1520/D2525-90R08.
4.2 Directions are given for calculating the number of such
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
sampling units required to give a preselected allowable varia-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tion at a stated probability level, or for calculating confidence
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. limitsforthesamplemeanobtainedforagivensizeofsample.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
D2525 − 90 (2008)
4.3 Directions are given for deciding which particular sam- the information in the sample results. In this case, the only
pling units should be chosen to constitute the required lot condition that applies is 6.1.3.
sample. These directions ensure that all potential sampling
unitshaveapproximatelythesamechanceofbeingselectedfor 7. Procedure
the lot sample.
7.1 Designate the form and size of the sampling unit,
bearing in mind the conditions and precautions discussed in
5. Significance and Use
Sections 5 and 6. Whenever possible, make the size of the
5.1 This recommended practice furnishes directions for the
sampling unit and specimen the same.
sampling of wool of the various forms indicated in Section 1,
7.1.1 The designation of the sampling unit depends on the
in order that correct probability statements may be made about
form of the material and on the method to be used for making
the relationship between the sample mean and the population
measurements on the sample. The material to be sampled may
mean. If these statements are to be correct, certain conditions,
existinoneofthreebasicforms:bulkmaterialsuchasscoured
which are stated, must hold.
wool or picked blends of wools, packaged material such as
5.2 Thisrecommendedpracticerequiresthatadeliberateact
baled wool, or material put up in the form of packages within
of randomization be performed so that all potential sampling
packagessuchasballsoftopwithincasesorbales.Themethod
units have approximately the same chance of being taken and
of measurement may require a specimen as large as a whole
no sampling unit is deprived of its chance of being taken.
package of material, or as small as a few grams of material.
5.3 In any case where insufficient information about the
7.1.2 Where the material to be sampled exists in some bulk
variability of the sampling units within the lot is available, form,suchasscouredwool,orablendthathasbeenpickedand
directions are given for calculating confidence limits for the
stored in a bin, the designation of a sampling unit will depend
samplemeansothatacorrectprobabilitystatementcanstillbe uponthemechanicsofdrawingthesample.Ifhandsamplingis
made.
the method employed, the sampling unit will be a handful of a
certain specified size. Whenever possible, the size of a sam-
6. Preliminary Conditions
pling unit should be made to coincide with the size of the
6.1 If it is desired to calculate a sample size to achieve a
specimen required by the method of measurement because the
preselected precision at a preselected level of confidence,
random variations observed in the test results are then directly
knowledge of the variation of the moisture content is neces-
applicable to the sampling units.
sary.
7.1.3 When the material to be sampled exists in the form of
6.1.1 The test method to be used must be the same method
packages such as baled wool or packages within packages,
that was used to derive any prior information with respect to
such as balls of wool top in cases or bales, the sampling unit
the variability of the moisture content.
can be either an entire package or some portion of a package,
6.1.2 The sampling unit must be the fundamental unit in
depending upon the size of the specimen required.
termsofwhichthevarianceisexpressed.Inotherwords,ifthe
7.2 Identify each potential sampling unit in the lot by
sampling unit is chosen to be a 25-g handful of bulk material
numbering, coding, using geometrical coordinates, or by any
ora4-yd(3.65-m)lengthofsliver,thenthevarianceusedmust
other systematic means. It is important that by some means or
be the number that expresses the variability of these units, and
other, all potential sampling units must be furnished with their
the number of sampling units which is calculated will be the
ownuniqueidentificationsothatnoneisdeprivedofitschance
number of such units required. The sampling unit is not
of being sampled.
necessarily the same thing as a specimen.
7.2.1 In designing a sampling plan, it is necessary to devise
6.1.3 The lot designated for sampling must be statistically
a method for assigning to every potential sampling unit in the
homogeneous.Thisisequivalenttosayingthatthelotshallnot
lot a unique identification. This is a relatively simple task in
be composed of a mixture of two or more parts, the moisture
thoseinstanceswherethesamplingunitsarediscretepackages,
contentofwhichisdistributedsufficientlydifferentlythatifthe
such as might be the case with balls of top if an entire ball is
moisture content of the entire lot were measured, a plot of the
to be the sampling unit.
moisture content versus the number of sampling units would
7.2.2 With material in bulk form or with packaged material
show a curve having more than one peak. (See Appendix X1.)
in which the sampling unit is to be only a portion of the
IfthetestgiveninAppendixX1leadstotheconclusionthatthe
package, it is not as easy to identify uniquely each potential
lot cannot be considered to be statistically homogeneous, then
sampling unit, and some method of approximating the ideal
itshouldbesubdividedintogroupsthatarehomogeneous.The
situation must be devised. See, for example, the instructions
pattern of runs found may indicate what the subgroups should
given in Practice D1060.
be.
7.2.3 For materials in loose bulk form, considerable inge-
6.1.4 The magnitude of the variation of moisture content
nuity and imagination may be required to effect a proper
within the homogeneous lot must be known.The magnitude of
identification of the potential sampling units.
the variation is usually expressed as the standard deviation,
although the range may also be used.
7.3 Option 1—This procedure is available for those in-
6.2 If insufficient knowledge is available to ensure meeting stanceswhereinformationissufficienttoenablethecalculation
the above conditions, a sample of convenient size may be of sample size required for a specified allowable variation and
selected and confidence limits calculated for the mean using probability level.
D2525 − 90 (2008)
7.3.1 If the allowable variation and probability level are not
Probability Level,% tt
stated in the applicable material specification or otherwise
90 1.645 2.706
established, determine for these factors values mutually agree-
95 1.960 3.842
able to all parties interested in the test results.
99 2.576 6.636
7.3.2 Wheneverthematerialbeingtestedhasbeenproduced
under statisically controlled conditions and records are
s = standarddeviationofindividualobservations,inunitsof
available, or information is available from prior tests on the
the property being evaluated, and
same lot, estimate the universe standard deviation from these
E = allowable variation of the test results expressed in units
data.
of the property being evaluated, which in some cases
may be a percentage.
NOTE2—Inmanyinstancesonlyanestimationofthevariationlikelyto
beencounteredinalotisavailable,suchasthelimitsbeyondwhichvalues
NOTE 3—The arbitrarily chosen value for E refers to the allowable
of moisture content are not likely to occur. Practice E122 includes variationinatestresultbasedonobservationsstilltobecarriedoutunder
formulas for estimating the standard deviation for different distributions
conditions of single-operator precision.
based on the extreme range of values expected. Whenever there is no
7.3.4 Using a table of random numbers or any satisfactory
information available as to the form of the distribution, assuming a
objective randomizing procedure, decide which particular po-
rectangular distribution will yield a relatively conservative estimate.
tential sampling units will make up the sample of the size
7.3.3 Based on values determined as directed in 7.3.1 and
calculated in 7.3.3.
7.3.2, calculate the number of sampling units required, using
7.3.5 Acquiretheseparticularsamplingunitsbythemethod
Eq 1 or Table 1:
required by the designation done in 7.1, using special care to
2 2 2
n 5 t 3s /E (1)
~ !
avoid gain or loss of moisture by the sampling unit in the
process of being taken. Weigh these sampling units as rapidly
where:
as possible as they are selected.
n = number of sampling units required rounded to the next
7.4 Option 2—This procedure is available for those in-
higher whole number when the calculated value of n is
equaltoorlessthan50androundedtothenexthighermultipleoffivewhenthe
stances where enough information to apply Option 1 is not
calculated value of n is greater than 50,
obtainable or for those instances where all parties interested in
t = constant depending on the desired probability level and
the results of the test agree to accept whatever precision may
equaltoStudent’stforinfinitedegreesoffreedomandtwo-sidedlimits,
resultfromanagreeduponfixedsamplesizeandprobabilityin
for example,
order to reduce the cost of testing.
7.4.1 Decide,byagreementbetweenthepartiesinterestedin
thetestresults,onthenumberofsamplingunitstobetakenand
the confidence level desired.
TABLE 1 Number of Sampling Units Required to Achieve an
7.4.2 Proceed as directed in 7.3.4 and 7.3.5.
Allowable Variation, E, at a Stated Probability Level, P,for
7.4.3 After performing the tests, calculate the confidence
Various Values of Universe Standard Deviation, σ
limits for the sample mean by Eq 2:
The listed values have been calculated by Eq 1.
Allowable Variation to beAchieved, E
Probability
Confidencelimits56ts/=n (2)
Level, P,.
0.25 0.5 0.75 1.0 1.25 1.5
where:
σ
0.25 0.80 2 1 1 1 1 1
n = number of sampling units in the sample,
0.90 3 1 1 1 1 1
t = valueofStudent’s t for n − 1 degrees of freedom, two-sided limits, and
0.95 4 1 1 1 1 1
the specification probability level, and
0.50 0.80 7 2 1 1 1 1
s = sample standard deviation, defined by Eq 3:
0.90 11 3 2 1 1 1
0.95 16 4 2 1 1 1
1/2
s 5 x 2 x¯ / n 21 (3)
@ ~ ! ~ !#
0.75 0.80 15 4 2 1 1 1
(i i
0.90 25 7 3 2 1 1
NOTE4—The xintheaboveequationareindividualvaluesforsampling
i
0.95 35 9 4 3 2 1
units when the sampling unit and the specimen are the same size. When,
1.00 0.80 27 7 3 2 2 1
however, more than one specimen is measured per sampl
...
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