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&EPA
United States
Environmental Protection
Agency
Environmental Monitoring
and Support Laboratory
P.O. Box 15027
Las Vegas NV89114
EPA-600/4-78-032
June 1978
Research and Development
Environmental
Monitoring Series
Environmental
Radioactivity Laboratory
Intercom pa rison
Studies Program
1978-1979
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S Environmental
Protection Agency, have been grouped into nine series. These nine broad categories
were established to facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields. The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL MONITORING senes.This series
describes research conducted to develop new or improved methods and instrumentation
for the identification and quantification of environmental pollutants at the lowest
conceivably significant concentrations. It also includes studies to determine the ambient
concentrations of pollutants in the environment and/or the variance of pollutants as a
function of time or meteorological factors
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161
-------
EPA-600/4-78-032
June 1978
ENVIRONMENTAL RADIOACTIVITY
LABORATORY INTERCOMPARISON STUDIES PROGRAM
1978-1979
by
Quality Assurance Branch
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
LAS VEGAS, NEVADA 89114
-------
DISCLAIMER
This report has been reviewed by the Environmental Monitoring and Support
Laboratory-Las Vegas, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
11
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FOREWORD
Protection of the environment requires effective regulatory actions
which are based on sound technical and scientific information. This
information must include the quantitative description and linking of pollutant
sources, transport mechanisms, interactions, and resulting effects on man and
his environment. Because of the complexities involved, assessment of specific
pollutants in the environment requires a total systems approach which trans-
cends the media of air, water, and land. The Environmental Monitoring and
Support Laboratory-Las Vegas contributes to the formation and enhancement of
a sound monitoring data base for exposure assessment through programs designed
to:
• develop and optimize systems and strategies for moni-
toring pollutants and their impact on the environment
• demonstrate new monitoring systems and technologies by
applying them to fulfill special monitoring needs of
the Agency's operating programs
This manual has been prepared to assist laboratories involved with
environmental radiation measurements in developing and maintaining a quality
control program and documenting the precision and accuracy of their data.
The intercomparison program described in this brochure should be of value to
the EPA, other Federal agencies, State agencies, and private laboratories.
For further information on matters related to the quality assurance of
environmental radiation measurements contact the Quality Assurance Branch,
Environmental Monitoring and Support Laboratory, Las Vegas, Nevada.
George'B. Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas
111
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ABSTRACT
An intercomparison studies program for laboratories involved in
environmental radiation measurements is conducted as part of the radiation
quality assurance program of the U.S. Environmental Protection Agency.
This brochure describes the types of environmental samples distributed,
the analyses required for each sample, the distribution schedule, and the
statistical analysis and reporting of results. Instructions and application
forms are included for laboratories desiring to participate in the program.
IV
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CONTENTS
Page
Foreword iii
Abstract iv
The Laboratory Intercomparison Studies Program 1
Types of Environmental Samples Distributed 2
Analysis of Data 3
Participation in the Laboratory Intercomparison
Studies Program 4
Statistical Calculations 14
Tables
1. Summary of Cross-check Programs 5
2. Cross-check Sample Distribution Schedule 6
3. Laboratory Precision: One Standard Deviation
Values for Various Analyses 7
Figures
1. Example of a results report form 8
2. Example of a sample analysis and report of participant's
data 10
3. Example of a control chart 12
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THE LABORATORY INTERCOMPARISON STUDIES PROGRAM
Environmental measurements of radiation are made daily by many Federal,
State, local, and private agencies. The data from these measurements are
used for a wide variety of purposes including assessment of health effects,
the establishment of standards and guides, and for enforcement activities.
It is therefore imperative that the precision and accuracy of the data be
assured in order that policy decisions concerning environmental quality are
based on valid and comparable data of known reliability.
In order to attain this goal, an Agency-wide quality assurance program
has been implemented within the U.S. Environmental Protection Agency (EPA).
In the area of radiation, quality control responsibilities have been assigned
to the Quality Assurance Branch at the EPA's Environmental Monitoring and
Support Laboratory-Las Vegas (EMSL-LV) which carries out a program designed to
encourage the development and implementation of quality control procedures for
sample collection, laboratory analysis, and data handling and reporting.
A major objective of this program is to assist laboratories involved in
environmental radiation measurements to develop and maintain both an intra-
laboratory and an interlaboratory quality control program. In part, this is
accomplished through an extensive laboratory intercomparison study ("cross-
check") program involving environmental media (milk, water, air, food, soil,
and gases) and a variety of radionuclides with activities at or near environ-
mental levels.
Simulated environmental samples, containing known amounts of one or more
radionuclides, are prepared and routinely distributed to laboratories
upon request. These laboratories perform the required analyses and return
their data to the Quality Assurance Branch for statistical analysis and
comparison with known values and analytical values obtained by other partici-
pating laboratories. A report and a control chart are returned to each
participant. The program thus enables each laboratory to document the pre-
cision and accuracy of its radiation data, identify instrument and procedural
problems, and to compare its performance with that of other laboratories.
Each laboratory making environmental measurements for radiation should
have an internal quality control program in operation to ensure that all
instrumentation is calibrated and functioning, and that analytical procedures
are being carried out properly. Such a program includes continual monitoring
of instrumentation, the plotting of instrument control charts, frequent
analysis of replicate samples to check precision, and the regular measurement
of samples to which known amounts of activity have been added to check the
accuracy of systems.
-------
Participation in a laboratory intercomparison study does not automatical-
ly assure the precision and accuracy ot a laboratory's data and should not be
considered as a substitute for a continuous quality control program within a
laboratory. Intercomparison data may be useful for documenting precision and
accuracy, and helping to indicate instrument or procedural problems. Par-
ticipation in intercomparison studies is useful in augmenting a laboratory's
quality control program by serving as a check on its internal quality control
program.
You are encouraged to have your laboratory participate or expand par-
ticipation in the cross-check program of the Quality Assurance Branch of the
EMSL-LVs Monitoring Systems Research and Development Division. A laboratory
may participate in any one or all of the studies described below.
TYPES OF ENVIRONMENTAL SAMPLES DISTRIBUTED
The current laboratory intercomparison studies program covers the analy-
sis of a variety of media containing various levels of radioactivity. These
include:
Water: Water containing several different mixtures of radioactive
materials is included in the cross-check program.
• Four-liter samples for the analysis of gross alpha and
gross beta activity are sent bimonthly to participating
laboratories.
Milk:
• Four-liter samples containing chromium-51, zinc-65,
cobalt-60, ruthenium-106, cesium-134, and cesium-137 are
distributed bimonthly for analysis of gamma emitters.
• Fifty-milliliter samples for tritium analysis are dis-
tributed on a bimonthly basis.
• Four-liter samples containing plutonium-239 are
shipped to laboratories twice a year.
• Four-liter samples containing radium-226
and radium-228 are distributed four times a year.
• Four-liter samples containing strontium-89, and
strontium-90 are distributed three times a year.
• Four-liter blind samples containing a mixture of the
above radionuclides are distributed semiannually.
Four-liter milk samples containing potassium, strontium-89,
strontium-90, iodine-131, cesium-137, and barium-140 are
distributed on a quarterly basis.
-------
Air: Two-inch diameter air filters are sent out on a quarterly basis
for gross alpha, gross beta, cesium-137, and strontium-90
analyses. Three air filters are sent to each laboratory.
Soil: Thirty-five-gram soil samples containing either plutonium-239
and plutonium-238, or thorium-228, thorium-230, and thorium-232
are each distributed once a year at 6-month intervals.
Diet: Four-liter food slurry samples containing strontium-89, stron-
tium-90, iodine-131, cesium-137, barium-140, and potassium are
sent to participants three times a year. Two samples are sent
to each laboratory.
Urine: Fifty-milliliter urine samples containing tritium are shipped
on a quarterly basis.
Gas: Ten-liter gas samples (S.T.P.) containing krypton-85 are distri-
buted annually in 1-liter steel cylinders.
Sample size, approximate activity levels, type of analysis, and other
pertinent information concerning the cross-check samples are summarized in
Table 1. The distribution schedule is outlined in Table 2.
ANALYSIS OF DATA
Each participating laboratory is expected to carry out three independent
determinations for each radionuclide included in a particular cross-check
study and to report its results on a form (Figure 1) provided with the
sample.
Upon receipt of the reports from all participating laboratories, the
data are transferred to punch cards for computer analysis. As indicated in
the sample calculations, this analysis includes determination of the labora-
tory standard deviation, calculation of the normalized range, normalized
deviation, sample standard deviation, and the grand average of all labora-
tories. The analytical precision values, used as a basis for judging labora-
tory performance for specific nuclides, are summarized in Table 3.
A report is generated containing data reported by participating labora-
tories, listed according to their identity code, along with the results of
the analysis (Figure 2). In addition, a control chart is generated and re-
produced for each radionuclide included in the sample (Figure 3). The
control charts are updated each time a laboratory participates in a particu-
lar cross-check study, thus giving each laboratory a continuous record of its
performance.
A letter giving the known value for each radionuclide is mailed to
participants approximately 2 weeks after the report due date. This is
followed by a complete report which includes a copy of the computer printout
and control chart.
-------
PARTICIPATION IN THE
LABORATORY INTERCOM?ARISON STUDIES PROGRAM
Any laboratory involved in, or concerned with, environmental radiation
monitoring and surveillance is eligible to participate in any one or all of
the studies described. Moreover, dependent upon personnel available and
their workload, a laboratory may elect to receive samples on a less frequent
basis than indicated on the distribution schedule (Table 2).
To become a participant in the laboratory intercomparison studies pro-
gram, complete one of the forms included at the end of this publication and
return to:
U.S. Environmental Protection Agency
Environmental Monitoring and Support Laboratory
Quality Assurance Branch
P.O. Box 15027
Las Vegas, NV 89114
Should the laboratory require additional types of cross-check samples at
some later date, a second form indicating the samples desired should be
submitted. There is no cost to participating laboratories for this service.
-------
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U.S. ENVIRONMENTAL PROTECTION AGENCY
ENVIRONMENTAL MONITORING AND
SUPPORT LABORATORY
P.O BOX 15027
LAS VEGAS. NEVADA 89114
702/736-2969
Laboratory
QUALITY ASSURANCE BRANCH
ANALYSIS RESULTS
TRITIUM IN URINE CROSS-CHECK PROGRAM
Contact Person
Phone
Collection Date
IMPORTANT: Report results corrected for decay as of the collection date.
Please refer to instructions on back of page.
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In order to be included in the final report, please send your results
no later than to:
U.S. Environmental Protection Agency
Environmental Monitoring and Support Laboratory
Quality Assurance Branch (MSQ)
P.O. Box 15027
Las Vegas, NV 89114
Figure 1. Example of a results report form
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REPORT SHEET INSTRUCTIONS
1. Legibly type or print numbers and letters in the proper squares. Use
only capital letters.
2. Record lab code in columns 1 and 2 for each isotope (one isotope per
line). For a code of only one letter, use column 1.
3. Slash the letters 0 and a. Do not slash any numbers.
4. Do not use columns 3-7; they are for internal use only.
5. Data entry: (columns 11-40)
a. All numbers must be right justified (entered to far right of
field).
b. For statistical purposes, it is important that each laboratory
report three results for each radionuclide. If, for some un-
avoidable reason, less than three values are reported, record
the data starting with the columns reserved for analysis #1
and work to the right.
c. Report results to the nearest whole number with the exceptions
of tritium and potassium Ceach recorded to multiples of ten)
and radium-226 (recorded to one decimal place) . Decimal points
are provided on the report forms.
d. Each line of the coding form contains the name of the isotope
and its unit of activity, preprinted for your convenience.
Each line should contain information pertaining to ;Just that
one isotope.
e. If a value is less than (3YT) the minimum detectable activity
(MDA), record LT, space, then the MDA value (right justified),
Figure 1 (continued). Results report form
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EMSL-LV TRITIUM IN URINE CROSS-CHECK PROGRAM SEPTEMBER 1974
09/20/74 SAMPLE - A 3H
KNOWN VALUE = 3273
EXPECTED LABORATORY PRECISION (IS, 1 DETERMINATION) = 357
LAB
AN
CF
CF
CF
CM
CM
CM
CO
z
z
z
PCI/L
PCI/L
D
D
D
J
J
J
3060
3060
3240
3255
3247
3294
EXPERIMENTAL
RESULT SIGMA
NO DATA PROVIDED
3269
3522
3632 186.1
3261
3373
3362 61.7
NO DATA PROVIDED
103.9
25.1
NO DATA PROVIDED
3240
3340
3190
RNG ANLY
(R + SR)
.60
.19
.30
.08
AVERAGE
3474
3332
3120
3265
NORMALIZED DEVIATION
(GRAND AVG) (KNOWN)
.9
.2
-.1
1.0
.3
— 7
-.0
76.4
.25
3257
-.2
-.1
EXPERIMENTAL SIGMA (ALL LABS) =
149
GRAND AVERAGE =
3290
Figure 2. Example of a sample analysis and report
of participant's data
10
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Explanation of terms in Figure 2:
Title: Program name, sample collection date, sample code letter,
analysis type, known concentration of radionuclide, expected
standard deviation of analysis - single determination.
Laboratory identification code (A, B, C, etc.).
Laboratory results (0-25 results listed down column).
Standard deviation (Is) of the experimental results.
Normalized range value in "mean range + standard error of
the range.. (£ + a} units for comparability. (See
R
Statistical Techniques for Quality Control of Environmental
Radioassay, AQCS Report Stat-1, November 1964, pages 4-8.)
(S = a for printing purposes.)
R R
Column 6: Average value.
Column 7 : Normalized deviation from the grand average value of all
laboratories expressed in a units.
m
Column 1:
Column 2:
Column 3:
Columns 4
and 5:
Bottom of
Chart:
Column 8: Normalized deviation from the known value expressed in a
m
units.
Experimental sigma (Is) of all laboratories, and the grand
average of all laboratories.
11
-------
10
9
8
7
6
5
4
3
1 J
01 1
0) 0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
R + 3
R + 2
R + 1
R + 0
0
EMSL— LV Tritium in Urine Crosscheck Program
Lab-D 3H
Normalized Deviation From Known
1976 1977
^*— ^^ \ /
V
S^
^^^
^0 — '
JFMAMJJASON DJFMAMJJASOND
Normalized Range
1976 1977
i • ill _|_
iii
CL
WL
WL
CL
f*i
UL
WL
JFMAMJ JASONDJFMAMJJASOND
Figure 3. Example of a control chart
12
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Explanations of terms used in the control chart (Figure 3).
Title:
Upper Graph:
Lower Graph:
Name of program, laboratory code letter, and type of
analysis.
"Normalized deviation from known versus the month
of analysis." [The 95.0% (y ± 2a ) and the 99.7%
m
(y ± 3o ) confidence levels were chosen as the warning
m
levels and control limits respectively.]
"Normalized range values (R + a ) versus the month of
R.
analysis." [The 97.5% (R + 2a ) and ^100% (R + 3a_)
R R
confidence levels were chosen as the warning levels
and control limits respectively.]
13
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STATISTICAL CALCULATIONS
To illustrate the computations performed by the computer, example calcu-
lations are given using data for three samples analyzed at one laboratory
(Laboratory p, see Figure 2).
The experimental data are listed and the mean, experimental sigma and
range are computed. These statistics provide measures of the central ten-
dency and dispersion of the data.
The normalized range is computed by first finding the mean range, R,
the control limit, CL, and the standard error ot tne range, a . The nor-
malized range measures the dispersion of the data (precision) in such a form
that control charts may be used. Control charts allow one to readily compare
past analytical performance with present performance. In the example, the
normalized range equals 0.3 which is less than 3, which is the upper warning
level. The precision of the results is acceptable.
The normalized deviation is calculated by computing the deviation and
the standard error of the mean, o . The normalized deviation allows one to
readily measure central tendency (accuracy) through the use of control charts.
Trends in analytical accuracy can be determined in this manner. For this
example, the normalized deviation is -0.7 which falls between +2 and -2,
which are the upper and lower warning levels. The accuracy of the data is
acceptable.
Finally, the experimental error of all laboratories, the grand average,
and the normalized deviation from the grand average are calculated in order
to ascertain the performance of all the laboratories as a group. Any bias in
methodology or instrumentation may be found from these results.
14
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EXAMPLE CALCULATIONS (Laboratory D Data, see Figure 2)
Experimental data:
Known value = y = 3273 pCi 3H/liter urine on September 24, 1974
Expected laboratory precision = a = 357 pCi/liter
Laboratory Sample Result
D
D
D
3060 pCi/liter
3060 pCi/liter
3240 pCi/liter
Mean = x
x =
= 3120 pCi/liter
where
N = number of results = 3
Experimental sigma = s
N
» * ZiXi
E <-> - ^1=1 '
i=l
N
s =
s =
N - 1
(3060)2 + (3060)2 + (3240)2 - (3°6° + 3°f + 22^
s = 103.9 pCi/liter
Range = r
r = I maximum result - minimum result
r = I 3240 - 3060 1 = 180 pCi/liter
15
-------
Range Analysis (RNG ANLY)*
Mean range = R
R = d2o
R
where
= 1.693 for N = 3
where D^**
= (1.693)(357)
R = 604.4 pCi/liter
Control limit = CL
CL = R + 3aR
= (2.575)(604.4)
CL = 1556 pCi/liter
Standard error of the range = CT
o = (R + 3a - R) r 3
R R
= (D^R - R) * 3
= (1556 - 604.4) v 3
R = 317.2 pCi/liter
Let range = r = wR + xaR = 180 pCi/liter
Define normalized range = w + x
for r > R, w = 1
then r = wR + xo^ = R + XOT
= 2.575 for N = 3
R
or
x =
r - R
therefore
w+x = 1 + x = 1 +
r - R
* Rosenstein, M., and A. S. Goldin, "Statistical Techniques for Quality Control
of Environmental Radioassay," AQCS Report Stat-1, U.S. Department of Health,
Education and Welfare, PHS, Nov 1964
** From table "Factors for Computing Control Limits," Handbook of Tables For
Probability and Statistics, 2nd Edition, The Chemical Rubber Co., Cleveland,
OH, 1968, p 454.
16
-------
for r < R, x = 0
then r = wR + XOR = wR
or
therefore w + x = w+0 = —
R
since r < R, (180 < 604.4)
180
w + x =
604.4
w + x = 0.30
Normalized deviation of the mean from the known value = ND
Deviation of mean from the known value = D
D = x - p
= 3120 - 3273
D = - 153 pCi/liter
Standard error of the mean =
a
m
_
a
357
m = 206.1 pCi/liter
ND = —
°m
- 153
206.1
ND = - 0.7
Control limit = CL
CL = (y ± 3om)
Warning Limit = WL
WL = (y ± 2a)
-------
Experimental sigma (all laboratories) = s. (See Figure 2)
st
14
st = 149 pCi/liter
Grand average = GA
N
r-v
GA =
N
49345
15
GA = 3290 pCi/liter
Normalized deviation from the grand average = ND1
Deviation of the mean from the grand average = D1
D' = x - GA
= 3120 - 3290
Di = - 170 pCi/liter
ND' = -
am
- 170
206.1
ND1 = - 0.8
*U.S. GOVERNMENT PRINTING OFFICE: 1978 - 785-922 Region No. 9-1
18
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SUBJECT: Participation in Intercomparison Studies Program
TO: U.S. Environmental Protection Agency
Environmental Monitoring and Support Laboratory
Quality Assurance Branch
P.O. Box 15027
Las Vegas, NV 89114
Please include our laboratory in the cross-check studies we have indicated
below. All samples are to be shipped to:
Contact Person
Title
Laboratory
Address
NRC License
and/or
Type(s)
State License Number(s)
NOTE: When requesting participation in a study containing either nuclear
byproducts or special nuclear materials, a copy of the NRC license(s)
must accompany the request.
Please indicate desired frequency of participation.
FREQUENCY DESIRED FREQUENCY DESIRED
>~ >J
HJ ij
>- >- -J <
i-J -J < 3
a: o: 3 z
H tU Z Z
! £ § ^
) — i ^_1 pf; fr]
z
z
ea C' H oo <
Milk: Sr
Water :
Gross a
Y
3H
239pu
225Ra,
Blind
89Sr, 9
I certify
,Y D
n
n
Diet:
UARTERLY
ex
Sr, Y
RIANNUALLY
EMIANNUALLY
H 00
DD
D
<^.
n
Air Filter:
, eD D
n n
DD
228Ra D
°Sr L
n
n
n
n
n
D
:n
this laboratory is
n
Q
n
n
n
n
n
Gross a , 3 1 1
137
Soil:
Pu
Th
Urine
Gases
authorized to
Cs , Sr
Isotopes
Isotopes
: 3H []
: 85Kr
receive the
n
n
samples
n
Q
Q
n
n
requested.
Signature
Date
Title
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-600/4-78-032
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
ENVIRONMENTAL RADIOACTIVITY LABORATORY INTERCOMPARISON
STUDIES PROGRAM, 1978-1979
5. REPORT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Quality Assurance Branch
Monitoring Systems Research and Development Division
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, NV 89114
10. PROGRAM ELEMENT NO.
1HD621
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency-Las Vegas, NV
Office of Research and Development
Environmental Monitoring and Support Laboratory
Las Vegas, NV 89114
13. TYPE OF REPORT AND PERIOD COVERED
interim 1978-1979
14. SPONSORING AGENCY CODE
EPA/600/07
15. SUPPLEMENTARY NOTES
16 ABSTRACT
The U.S. Environmental Protection Agency's intercomparison studies program for
laboratories involved in environmental radiation measurements is described. The
types of environmental samples distributed, the analyses required for each sample,
the distribution schedule, and the statistical analysis and reporting of results
are discussed. Instructions and application forms are included for laboratories
desiring to participate in the program.
This document is not a research report. It is designed for use by laboratories
participating or desiring to participate in the quality assurance program.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
quality assurance
quality control
quantitative analysis
radioactivity
statistical quality control
07 B, E
12 A
14 D
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
28
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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