ASTM Designation: D 6518 – 03aPDF Free Download

Standard Practice for
Bias Testing a Mechanical Coal Sampling System:

This standard is issued under the fixed designation D 6518; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon ( e ) indicates an editorial change since the last revision or reapproval.

1. 

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3.2.10 reference sample
, n
—a sample used in testing of a
mechanical sampling system which is comprised of one or
more increments collected from the test batch or lot of coal by
the stopped belt method as described in Practice D 2234.
3.2.11 reject stream
,n
—the coal flow within a mechanical
sampling system, which occurs at each stage of division, before
and after reduction, and is not included in the system sample.
3.2.12
save stream
,
n
—the coal flow within a mechanical
sampling system which occurs at each stage of division, before
and after reduction, and after the final stage of division
becomes the system sample.
3.2.13
statistical independence
,
n
—two sample values are
statistically independent if the occurrence of either one in no
way affects the probability assigned to the occurrence of the
other.
3.2.14
surrogate sample
,
n
—a sample, used in the evalua-
tion of a mechanical sampling system, which is comprised of
one or more increments collected from a coal stream within the
mechanical sampling system in accordance with Practice
D 2234, Conditions “A” or “B.” Such a sample may be
considered acceptable for evaluation of a mechanical sampling
system’s components, excluding the primary cutter, when
demonstrated to be equivalent to the reference sample.
3.2.15
system sample
,
n
—a sample collected from a test
batch or lot of coal by the mechanical sampling system being
tested for bias.
3.2.16
Walsh averages
,
n
—given a series of observations
(differences)
x 1, x
2, ... xn
, the n ( n
+ 1)/2 pair-wise averages
given by:
~ xi 1 xj ! /2, 1 #
i # j # n (1)3.2.16.

Discussion:

—As an example of Walsh averages,
assume one has three observations (differences) designated as
x
1,
x
2, and
x
3. There are then a total of 3(4)/2 = 6 Walsh
averages. They are as follows:

x  1, x 2, x 3, ( x 1+ x 2)/2, ( x 1+ x 3)/2, and ( x 2+ x 3)/2. 3.2.17
Wilcoxon Signed Rank Test
,
n
—a non-parametric
statistical procedure for calculating the point estimate and
confidence interval for a sample drawn from a population with
symmetric distribution.