United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/600/R-98/059
May 1998
&EPA
Iodine in Water Performance
Evaluation Study
A Statistical Evaluation of the
February 6, 1998 Data
006ECB98COV-059
-------
Iodine in Water
Performance Evaluation Study
February 6, 1998
Environmental Protection Agency
National Exposure Research Laboratory
Environmental Sciences Division
Las Vegas, Nevada
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
ENVIRONMENTAL SCIENCES DIVISION-LAS VEGAS
P.O. BOX 93478
LAS VEGAS. NEVADA 89193-3478
(702/798-2100)
Dear Participant,
Enclosed are the results of the Environmental Sciences Division (ESD-LV)
Performance Evaluation Study for Iodine in Water; February 6, 1998.
The known value for each analysis was determined by gravimetric methods,
checked by chemical analyses performed by ESD-LV's Radiochemistry Laboratory,
and compared to the participating laboratories' grand average.
The expected precision, determined by the known value, was taken from
"Table 3. Laboratory Precision: One Standard Deviation Values and Control Limits
for Various Analyses", which is based on data accumulated over the years by the
Performance Evaluation Program, and can be found in the Environmental Radioactivity
Performance Evaluation Studies Program and Radioactive Standards Distribution
Program information brochure.
Please take a few minutes to review this report and the analytical data your
laboratory submitted to us. If there are any apparent discrepancies, please notify us
immediately.
We encourage you to make use of the computer-automated data-entry system
that has been in place for some time now. As the number of participants increases,
and it becomes unrealistic for us to receive results by mail or FAX, the computer
system will be our only avenue for accepting data.
If you have any questions or comments, please send a message via the data-entry
system or contact Stephen Pia at 702/798-21 02 or Patricia Honsa at 702/798-21 41 .
Sincerely,
Stephen Pia
Team Leader
RADQA Program
Enclosure
-------
NOTICE
This material has been funded wholly by
the U.S. Environmental Protection Agency.
It has been subjected to the Agency's review,
and has been approved for publication as
an EPA document.
-------
ESD-LV Performance Evaluation: Iodine in Water, 6-Feb-1998 1/7
The following pages consist of separate sections for each of the nuclides in this study with four
parts per section. After the first, each part is separated from the next by a new page or a thick
horizontal bar. The first page of each section is a statistical summary for the nuclide and starts
with a statement of the known value, the control limits, and the warning limits.
The warning limits are placed at two normalized standard deviations above and below the
known value and the control limits are three normalized standard deviations above and below
the known value. If you keep control charts, these values will be useful for anticipating problems
with the accuracy of your analytical methods.
The coin shaped pie chart at the top of the summary page shows the fate of all the samples
sent out in number and percentage terms. The pie chart starts at the top and rotates clockwise.
The first sector represents those participants who submitted analytical results within both the
warning and control limits. The next sector represents those who are in the warning region but
not out of control. The third sector represents those who are out of control, but have passed
the outlier test. The fourth sector represents those who have failed the outlier test. The last
sector represents those participants who have failed to respond properly. This is the case if no
analytical results were returned, or less than three determinations were reported, or if the results
were received too late. The reeding on the edge of the coin is spaced at one percent intervals, and
the sector shading becomes darker as the data reliability decreases. Sectors with zero width are
not shown.
The table in the center shows a number of statistical quantities calculated from the submitted
data based on the mean and median values in relation to the known value, both before and after
outlier removal. The lower pie chart uses the same construction as the upper chart and shows
the distribution of properly submitted data in terms of deviation from the known value divided
into sectors representing one, two, three, and greater than three normalized standard deviations.
The second part is an alphabetical listing, in lab-code order, of submitted data and several
calculated quantities. An entry that is shaded has been rejected because of one of the reasons
listed above or failure of the outlier test. The fifth and sixth columns are a measure of laboratory
precision. The Range analysis is a normalized value that you may use to keep precision control
charts. The eighth and ninth columns are the differences from the mean of all non-outliers and
from the known value, respectively. If this value is between 2.0 and 3.0, your analytical process
precision is in the warning zone; if it exceeds 3.0 it is out of control. A tag symbol may appear in
the last column. Each page with tags has a symbol definition summary at the bottom. If there is
no tag symbol, the data is within the control limits, but it may be in the warning zone.
The third part is a three-column listing of result average, tag symbol, and lab-code in average
order excluding those labs not responding properly. In this order, all outliers and out-of-control
results appear at the top or bottom of the list.
The last part is two bar chart displays showing frequency distributions of responding
participants. The first chart places the known value at the center and a bar at each 0.2 unit of
expected precision. The second chart places the mean of the reported measurements at the center
and a bar at each 0.2 unit of standard deviation. In both cases, a bar includes those results within
0.1 unit up to the maximum of six. Any results more than six units from the center value are
shown cumulatively by a shaded bar one past the sixth unit. If the central tendency of the known
value distribution falls away from the center, an error in accuracy is indicated. If the distribution
is broad, poor precision is indicated. The mean value distribution is similar but uses the average
and standard deviation of reported results as its basis.
-------
2/7
ESD-LV Performance Evaluation: Iodine in Water, 6-Feb-1998
The Range Analysis(R + SR) is calculated from the range, mean range and standard error of
the range values. The range is the difference between the maximum and minimum results for the
laboratory. The mean range is calculated by multiplying the expected precision by 1.693(for three
results). The standard error of the range is calculated by multiplying the mean range by 2.575(for
three results), subtracting the mean range from this product, and dividing the result by 3. If the
range is greater than the mean range, then the range analysis is calculated by subtracting the
mean range from the range, dividing the result by the standard error of the range and adding 1.
If the mean range is greater than or equal to the range, then the range analysis is calculated by
dividing the range by the mean range.
The normalized deviation of the mean from the grand average is calculated from the deviation
of the mean from the grand average and the standard error of the mean values. The deviation of
the mean from the grand average is calculated by subtracting the grand average from the
average of the laboratory's three results. The standard error of the mean is calculated by
dividing the expected precision by the square root of 3(the number of results). The normalized
deviation of the mean from the grand average is calculated by dividing the deviation of the mean
from the grand average by the standard error of the mean.
The normalized deviation of the mean from the known value is calculated from the deviation of
the mean from the known value and the standard error of the mean values. The deviation of the
mean from the known value is calculated by subtracting the known value from the average of the
laboratory's three results. The standard error of the mean is calculated by dividing the expected
precision by the square root of 3(the number of results). The normalized deviation of the mean
from the known value is calculated by dividing the deviation of the mean from the known value by
the standard error of the mean.
A complete explanation of the statistical calculations involved in the report may be found in
the Environmental Radioactivity Performance Evaluation Studies Program information brochure
[Draft Revision of EPA-600/4-81-004], available from Patricia Honsa, ESD-LV, 702/798-2141.
-------
ESD-LV Performance Evaluation: Iodine in Water, 6-Feb-1998
3/7
Iodine-131 Statistical Summary 107 Participants
The known value of this nuclide is 104.9 pCi/1 with an expected precision of 10.5; the control limits
are 86.7 to 123.1; the warning regions are 86.7 to 92.7 and 117.1 to 123.1
24(22.4 %) Failed to respond
2(1.9 %) Outliers '
Statistic
. 77(72.O %) Within all limits
Respondents
4(3.7 %) In warning zone
but within control
Non-outliers
Mean
Std. Dev.
Variance
%Coef. ofVar.
% deviation of mean from known value
Norm. dev. of mean from known value
Median
% deviation of median from known value
Norm. dev. of median from known value
104.94 Grand Avg 105.74
7.39 5.43
54.59 29.50
7.04 5.14
0.04 0.80
0.01 0.15
104.83 105.00
-0.06 0.10
-0.01 0.02
2(2.4 %) More than 3 norm. S.D. ».^
4(4.8 %) Between 2 and 3 norm. S.D. •
63(75.9 %) Within 1 norm. S.D.
of known value
14(16.9 %) Between 1 and 2 norm. S.D.
-------
fi, — . .
4/7
ESD-LV Performance Evaluation: Iodine in Water, 6-Feb-1998
Iodine-131
Lab
A
AF
AJ
AK
AL
AP
AU
AW
AY
AZ
BA
BC
BH
BK
BL
BM
BO
C
CA
CC
CE
CJ
CP
cs
ex
D
DD
DE
DR
DT
DY
E
EB
EH
EL
EX
FE
FL
GI
HE
HK
HP
I
LA
IU
• =
0 3
Res. 1
107.2
107.2
105.5
107.6
102.4
104.2
96.4
112.4
115.0
104.1
109.0
106.0
97.0
108.6
104.0
103.0
110.1
98.2
110.0
116.6
103.3
108.9
104.0
103.0
107.0
107.0
103.2
104.0
122.0
109.7
94.3
«-
109.0
103.8
111.1
99.4
122.0
107.1
107.0
Res. 2
106.9
108.1
98.0
107.8
106.7
102.9
102.7
116.7
114.0
100.7
107.0
104.0
103.7
105.6
104.0
102.0
111.4
103.8
110.0
116.7
100.0
107.2
107.0
104.0
107.0
102.0
107.4
104.0
92.0
106.8
107.0
106.0
107.4
120.7
99.6
111.0
102.9
110.0
Res. 3
107.1
107.6
99.3
109.3
101.2
101.6
96.1
116.9
111.0
102.4
113.0
105.0
110.5
108.4
107.0
104.0
111.8
98.1
110.0
104.3
104.2
110.1
105.0
104.0
111.0
109.0
98.9
105.0
105.0
110.2
92.2
112.0
101.4
116.8
99.5
110.0
104.5
107.0
No data submitted
Insufficient
data
x =
Exper.
1
Rng anal Normalized deviation
Sigma (R + SR) Average (grand-avg) (known) Tag
0.15
0.45
4.01
0.93
2.89
1.30
3.73
2.54
2.08
1.70
3.06
1.00
6.75
1.68
1.73
1.00
0.89
. ••' V
3.26
0.00
7.13
2.21
1.46
1.53
0.58
2.31
3.61
4.25
0.58
15.04
1.84
8.01
3.00
3.02
4.83
0.10
6.66
2.12
1.73
0.017
0.051
0.422
0.096
0.309
0.146
0.371
0.253
0.225
0.191
0.338
0.113
0.759
0.169
0.169
0.113
0.096
•;„.,.•>
0.321
0.000
0.698
0.236
0.163
0.169
0.056
0.225
0.394
0.478
0.056
2.310
0.191
0.833
0.338
0.338
0.540
0.011
0.675
0.236
0.169
107.07
107.63
100.93
108.23
103.43
102.90
98.40
115.33
113.33
102.40
109.67
105.00
103.73
107.53
105.00
103.00
111.10
100.03
110.00
112.53
102.50
108.73
105.33
103.67
108.33
106.00
103.17
104.33
106.33
108.90
97.83
109.00
104.20
116.20
99.50
114.33
104.83
108.00
TAG SYMBOLS
Determined
to be an
outlier
0.22
0.31
-0.79
0.41
-0.38
'
-0.47
-1.21
1.58
1.25
-0.55
0.65
-0.12
-0.33
0.30
-0.12
-0.45
0.88
-0.94
0.70
1.12
-0.53
0.49
-0.07
-0.34
0.43
0.04
-0.42
-0.23
0.10
0.52
-1.30
0.54
-0.25
1.73
-1.03
1.42
-0.15
0.37
It = Above
JJ. = Below
0.36
0.45
-0.65
0.55
-0.24
*-
-0.33
-1.07
s"-
• ; •
1.72
1.39
-0.41
0.79
0.02
-0.19
0.43
0.02
-0.31
1.02
•
-0.80
0.84
1.26
•
-0.40
0.63
0.07
-0.20
0.57
0.18
• •
-0.29
-0.09
0.24
0.66
-1.17
• •
0.68
-0.12
1.86
-0.89
1.56
-0.01
•
0.51
control limit
control limit
-------
ESD-LV Performance Evaluation: Iodine in Water, 6-Feb-1998
Iodine-131
Lab Res. 1
J
JR
JS
JY
K
KL
KM
KX
L
LF
LT
M
MN
MP
MV
N
NJ
NO
0
OA
OB
OT
PB
PE
PW
Q
QX
QY
QZ
R
RK
S
sc
SD
SM
ss
sv
sz
TA
TC
TD
TF
TL
TQ
U
• =
0 =
117.0
126.0
101.2
106.7
95.7
100.0
103.7
100.0
104.0
85.0
100.0
107.0
' •: , • '''"•'
102.4
98.0
84.4
110.0
106.1
110.6
119.7
104.5
108.0
100.4
101.2
102.0
120.0
105.6
110.0
101.4
106.6
114.8
99.0
106.9
108.6
102.4
76.1
101.9
°*
s
105.0
101.3
Res. 2
120.0
111.0
108.5
106.8
98.1
101.0
102.7
100.0
104.0
90.0
106.0
105.0
'' :". '•'. ••••: " '-.: '
103.4
106.0
93.2
107.0
101.4
111.6
116.7
102.7
96.0
100.0
95.8
100.0
120.0
103.3
117.0
103.1
107.9
103.7
104.8
107.4
103.5
95.9
67.5
105.1
•>
107.0
110.2
Res. 3
119.0
109.0
97.3
103.7
98.8
101.0
100.2
110.0
107.0
87.0
101.0
100.0
• ;' .:. v . .
103.9
106.0
102.1
109.0
105.6
103.3
121.8
105.0
110.0
103.3
96.5
100.3
115.0
103.0
115.0
105.1
109.0
107.6
109.5
104.1
106.8
113.2
76.7
105.3
115.0
104.0
No data submitted
Insufficient
data
X 3
Exper.
Sigma
1.53
9.29
5.69
1.76
1.63
0.58
1.80
5.77
1.73
2.52
3.21
3.61
0.76
4.62
8.85
1.53
2.58
4.53
2.56
1.21
7.57
1.80
2.94
1.08
2.89
1.42
3.61
1.85
1.20
5.63
5.26
1.78
2.59
8.74
5.15
1.91
5.29
4.56
5/7
Rng anal Normalized deviation
(R + SR) Average (grand-avg) (known) Tag
0.169
0.956
0.630
0.174
0.174
0.056
0.197
0.563
0.169
0.281
0.338
0.394
0.084
0.450
0.996
0.169
0.264
0.467
0.287
0.129
0.788
0.186
0.304
0.113
0.281
0.146
0.394
0.208
0.135
0.624
0.591
0.186
0.287
0.973
0.518
0.191
0.563
0.501
118.67
115.33
102.33
105.73
97.53
100.67
102.20
103.33
105.00
87.33
102.33
104.00
103.23
103.33
93.23
108.67
104.37
108.50
119.40
104.07
104.67
101.23
97.83
100.77
118.33
103.97
114.00
103.20
107.83
108.70
104.43
106.13
106.30
103.83
73.43
104.10
109.00
105.17
TAG SYMBOLS
Determined
to be an
outlier
2.13
1.58
-0.56
0.00
-1.35
-0.84
-0.58
-0.40
-0.12
-3.04
-0.56
-0.29
-0.41
-0.40
-2.06
0.48
-0.23
0.46
2.25
-0.28
-0.18
-0.74
-1.30
-0.82
2.08
-0.29
1.36
-0.42
0.35
0.49
-0.22
0.07
0.09
-0.31
-5.33
-0.27
0.54
-0.09
ft 3 Above
U = Below
•
*
2.27
1.72
-0.42
0.14
-1.22
-0.70
-0.45
-0.26
0.02
-2.90
-0.42
-0.15
-0.27
-0.26
-1.92
0.62
-0.09
0.59
2.39
-0.14
....:... . ,-.* •
-0.04
-0.60
-1.17
-0.68
2.22
-0.15
1.50
-0.28
•
0.48
0.63
-0.08
0.20
0.23
-0.18
-5.19 x
-0.13
«•
*
0.68
0.04
control limit
control limit
-------
6/7 ESD-LV Performance Evaluation: Iodine
Iodine-131
Lab Res. 1 Res. 2
UC
ui
UM
UP 108.0 106.0
UY 110.0 110.0
VA
VC
VM 100.0 100.0
VN 110.5 109.7
W
WM
WO 60.0 70.8
X 99.1 102.5
XK
XO
XQ
Y 111.0 102.0
Exper.
Res. 3 Sigma
110.0 2.00
111.0 0.58
100.0 0.00
113.2 1.83
85.8 12.96
106.5 3.70
103.0 4.93
Rng anal
(R 4- SR)
0.225
0.056
0.000
0.197
1.860
0.416
0.506
in Water, 6-Feb-1998
Normalized deviation
Average (grand-avg) (known)
108.00 0.37 0.51
110.33 0.76 0.90
! *
100.00 -0.95 -0.81
111.13 0.89 1.03
72.20 -5.53 -5.39
102.70 -0.50 -0.36
105.33 -0.07 0.07
A
Tag
•
• • i-
•
•
»'
•
•
x
»
•
•
Data sorted by Laboratory Average
Average Tag
72.20 x
73.43 x
87.33
93.23
97.53
97.83
97.83
98.40
99.50
100.00
100.03
100.67
100.77
100.93
101.23
102.20
102.33
102.33
102.40
102.50
102.70
102.90
103.00
103.17
103.20
• = No data submitted
0 = Insufficient data
V-
Lab
WO
TC
M
NO
KM
QX
EX
AW
HK
VM
CE
KX
QY
AJ
Q
L
MN
K
BC
CX
X
AU
C
E
S
Average
103.23
103.33
103.33
103.43
103.67
103.73
103.83
103.97
104.00
104.07
104.10
104.20
104.33
104.37
104.43
104.67
104.83
105.00
105.00
105.00
105.17
105.33
105.33
105.73
106.00
Tag
TAG SYMBOLS
Lab
N
NJ
LF
AL
DE
BL
TA
R
MP
PB
TD
GI
EB
OA
SS
PW
I
LT
BO
BK
U
Y
DD
KL
DT
Average Tag
106.13
106.30
106.33
107.07
107.53
107.63
107.83
108.00
108.00
108.23
108.33
108.50
108.67
108.70
108.73
108.90
109.00
109.00
109.67
110.00
110.33
111.10
111.13
112.53
113.33
ft = Above control
x = Determined to be an outlier li = Below control
Lab
SV
sz
EH
A
BM
AF
SD
UP
IU
AK
DR
OB
O
SM
D
EL
TQ
FL
BH
CJ
UY
CA
VN
CP
BA
limit
limit
'
-------
ESD-LV Performance Evaluation: Iodine in Water, 6-Feb-1998
7/7
Iodine-131
Average
Tag
Data sorted by Laboratory Average
Lab Average Tag Lab | Average
Tag
Lab
114.00
114.33
RK
HP
115.33
115.33
116.20
JY
AZ
HE
118.33
118.67
119.40
QZ
JS
OT
% responding labs
Frequency distribution
10
-4 -2 0 +2 +4
Normalized deviation of the mean from the known value
% responding labs
Frequency distribution
-6
-4 -20+2 +4
Normalized deviation of the mean from the grand average
• 3 No data submitted
0 = Insufficient data
TAG SYMBOLS
x = Determined to be an outlier
It = Above control limit
II = Below control limit
------- |