United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
P.O. Box 93478
Las Vegas NV 89193-3478
EPA/600/R-92/192
October 1992
Research and Development
&EPA Iodine in Water
Intercomparison Study
A Statistical Evaluation of the
August?, 1992 Data
5168GR92NRD-19
-------
Iodine in Water
Intercomparison Study
August 7, 1992
Environmental Protection Agency
Environmental Monitoring Systems Laboratory
Las Vegas, Nevada
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY-LAS VEGAS
P.O. BOX 93478
LAS VEGAS, NEVADA 89193-3478
(702/798-2100)
Dear Participant,
Enclosed are the results of the Nuclear Radiation Assessment Division (EMSL-LV)
Intercomparison Study for Iodine In Water; August 7, 1992.
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 Frank Novielli at 702/798-2159 or Patricia Honsa at 702/798-2141.
Sincerely,
Frank Novielli
Senior Chemist
Radioanalysis Branch
Enclosure
-------
NOTICE
This material has been funded wholly by
the U.S. Environmental Protection Agency.
It has been subject to the Agency's review,
and it has been approved for publication
as an EPA document.
-------
EMSL-LVIntel-comparison Study: Iodine in Water, 7-Aug-1992 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. 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. The eighth and ninth columns are the differences from
the mean of all non-outliers and from the known value, respectively. 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.
-------
EMSL-LV Intel-comparison Study: Iodine in Water, 7-Aug-1992
2/7
Iodine-131 Statistical Summary 127 Participants
The known value of this nuclide is 45.0 pCi/1 with an expected precision of 6.0; the control limits
are 34.6 to 55.4; the warning regions are 34.6 to 38.1 and 51.9 to 55.4
22(17.3 %) Failed to respond -,
12(9.4%) Outliers'
2(1.6 %) Out of control '
but not an outlier
Statistic
. 85(66.9 %) Within all limits
Respondents
*• 6(4.7'%) In warning zone
but within control
Non-outliers
Mean
Std. Dev.
Variance
% Coef. of Var.
% 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
53.28
54.67
2988.31
102.61
18.39
0.15
45.67
1.48
0.01
Grand Avg 45.91
3.79
14.40
8.27
2.02
0.24
45.33
0.74
0.09
14(13.3 %) More than 3 norm. S.D. ,
6(5.7 %) Between 2 and 3 norm. S.D.'
66(62.9 %) Within 1 norm. S.D.
of known value
• 19(18.1 %) Between 1 and 2 norm. S.D.
-------
3/7 EMSL-LV Intel-comparison Study: Iodine in Water, 7-Aug-1992
Iodine-131
Lab
A
AA
AF
AI
AJ
AK
AL
AN
AP
AU
AW
AY
AZ
BA
BC
BH
BL
BM
BO
BW
C
CA
CE
CJ
CP
CQ
D
DD
DE
DG
DL
DM
DR
DT
DY
E
EB
EH
EL
EX
BZ
FB
FK
FL
FU
• =
0 =
Res. 1
45.0
Sf '&" '
42.0
44.0
46.0
45.0
42.0
48.0
43.0
50.0
07v0
44.0
45.0
38.0
54.0
50.0
41.0
45.0
41.0
49.0
45.0
48.0
46.0
49.0
49.0
49.0
43.0
45.0
41.0
50.0
43.0
50.0
54.0
39.0
46.0
45.0
48.0
49.0
46.0
45.0
3U&
•• f}'d{\ •f^L-
jaCf'v^'ij
§B$
46.0
37.0
Res. 2
44.0
', &&* '
45.0
48.0
45.0
46.0
43.0
50.0
46.0
43.0
07.0
47.0
47.0
40.0
56.0
48.0
45.0
45.0
45.0
49.0
44.0
48.0
54.0
44.0
51.0
50.0
47.0
43.0
42.0
55.0
43.0
46.0
49.0
43.0
45.0
45.0
46.0
44.0
48.0
45.0
10
280.0
_,
48.0
47.0
Res. 3
44.0
63.0
44.0
58.0
47.0
44.0
40.0
47.0
43.0
42.0
$4,0'
37.0
60.0
44.0
58.0
48.0
43.0
45.0
44.0
50.0
46.0
45.0
52.0
37.0
51.0
46.0
45.0
47.0
42.0
47.0
43.0
51.0
51.0
55.0
43.0
44.0
47.0
46.0
50.0
46.0
, t.$
270*0
49.0
48.0
No data submitted
Insufficient
data
x =
Exper.
Sigma
0.58
&0&
1.53
7.21
1.00
1.00
1.53
1.53
1.73
4.36
O3-
5.13
8.14
3.06
2.00
1.15
2.00
0.00
2.08
0.58
1.00
1.73
4.16
6.03
1.15
2.08
2.00
2.00
0.58
4.04
0.00
2.65
2.52
8.33
1.53
0.58
1.00
2.52
2.00
0.58
0.00
10JJO
1.53
6.08
Rnganal
(R + SR) Average
0.098
0.984
0.295
1.720
0.197
0.197
0.295
0.295
0.295
0.788
0,£$&
0.984
1.908
0.591
0.394
0.197
0.394
0.000
0.394
0.098
0.197
0.295
0.788
1.345
0.197
0.394
0.394
0.394
0.098
0.788
0.000
0.492
0.492
2.095
0.295
0.098
0.197
0.492
0.394
0.098
0*000
2.846
0.295
1.158
44.33
, 4ftJtt
43.67
50.00
46.00
45.00
41.67
48.33
44.00
45.00
$1,00
42.67
50.67
40.67
56.00
48.67
43.00
45.00
43.33
49.33
45.00
47.00
50.67
43.33
50.33
48.33
45.00
45.00
41.67
50.67
43.00
49.00
51.33
45.67
44.67
44.67
47.00
46.33
48.00
45.33
iJ00
370,00
47.67
44.00
TAG SYMBOLS
Determined
to be an
outlier
Normalized deviation
(grand-avg) (known) Tag
-0.46
4J4
-0.65
1.18
0.03
-0.26
-1.23
0.70
-0.55
-0.26
5J0
-0.94
1.37
-1.51
2.91
0.80
-0.84
-0.26
-0.74
0.99
-0.26
0.31
1.37
-0.74
1.28
0.70
-0.26
-0.26
-1.23
1.37
-0.84
0.89
1.57
-0.07
-0.36
-0.36
0.31
0.12
0.60
-0.17
*tttd$
64,6$
'
0.51
-0.55
ft s Above
-0.19
5.00 X
-0.38
1.44
0.29
0.00
-0.96
0.96
-0.29
0.00
6x00 X
-0.67
1.64
-1.25
3.18 ft
1.06
-0.58
0.00
-0.48
1.25
0.00
0.58
1.64
-0.48
1.54
0.96
0.00
0.00
-0.96
1.64
-0.58
1.15
1.83
0.19
-0.10
-0.10
0.58
0.38
0.87
0.10
-12.70 X
64.06 X
®
0.77
-0.29
control limit
U s Below control limit
-------
EM8L-LV Intercomparison Study: Iodine in Water, 7-Aug-1992
4/7
Iodine-131
Lab
GE
GI
HJ
HK
HP
I
IA
1C
IU
J
JR
JS
K
KL
KX
L
LF
LR
M
MA
ME
ML
MN
MP
MQ
MS
MV
N
-ftfit
NJ
JNV
O
OA
OB
OM
or
PB
FC
,P-3§
PT
Pt?
PV
Res. 1
43.0
51.0
46.0
45.0
'"'/Aid''
45.0
42.0
44.0
47.0
46.0
44.0
46.0
682.0 ,
47.0
'
45.0
45.0
52.0
45.0
35.0
49.0
40.0
f f f
47.0
47.0
50.0
44.0
42.0
", '840'
44.0
'-''':'"' ' ' -'"'
43.0
46.0
46.0
'
. 63.0
50.0
/ f
, ' r
33.0
f*y>
43.0
Res. 2
43.0
56.0
40.0
45.0
ZJS
41.0
37.0
45.0
44.0
45.0
44.0
50.0
ftSUJ
46.0
f
42.0
42.0
53.0
44.0
37.0
45.0
52.0
f f
43.0
47.0
51.0
38.0
43.0
•': S&0
44.0
''"'',* '' > ',',
43.0
47.0
42.0
,
4#.0
48.0
"
'
35.0
&7.0
45.0
Res. 3
43.0
50.0
57.0
46.0
-** ''- , r: -
"';..'. 16
50.0
34.0
46.0
47.0
46.0
44.0
45.0
"- 6i$tO -
46.0
- ', -'
44.0
45.0
50.0
44.0
39.0
43.0
46.0
/ ? '
43.0
51.0
49.0
41.0
42.0
^'-''•i&O *
43.0
'''*~W '"
43.0
45.0
41.0
> 6&0
46.0
t ' '
,
36.0
•- •-." BS.O
46.0
• = No data submitted
0 =
Insufficient
data
V -—
Exper.
Sigma
0.00
3.21
8.62
0.58
'-^w>£
4.51
4.04
1.00
1.73
0.58
0.00
2.65
4.1^'
0.58
1.53
1.73
1.53
0.58
. 2.00
3.06
6.00
; ,
2.31
2.31
1.00
3.00
0.58
18.36
0.58
- ' '
0.00
1.00
2.65
_,
,3*51
2.00
1.53
12J3
1.53
Rng anal
(R + SR)
0.000
0.591
2.283
0.098
' ,/
0.886
0.788
0.197
0.295
0.098
0.000
0.492
0.788
0.098
"
0.295
0.295
0.295
0.098
0.394
0.591
1.345
'
0.394
0.394
0.197
0.591
0.098
;&4?$"
0.098
'
0.000
0.197
0.492
-------
5/7
Iodine-131
Lab Res. 1
PW
Q 46.0
QK 46.0
QU 7£0
QX 52.0
QZ
R 44.0
RC 54.0
RM 54.0
EH 19.0
HQ 86.0
S 45.0
SD
SF 45.0
SI
SK 43.0
am
SS 45.0
sr
SW 46.0
ST
SZ 53.0
TA 45.0
TK '
TO
TI 49.0
TL 54.0
TQ 41.0
TR 52.0
"IS
TV 46.0
U 45.0
W
X 41.0
Y 46.0
Z 50.0
EM8L-LV
Res. 2
,
46.0
48.0
mo
53.0
43.0
49.0
50.0
24&
86.0
45.0
45.0
42.0
44.0
-
52.0
,
52.0
45.0
44.0
63.0
40.0
46.0
"
38.0
37.0
45.0
48.0
44.0
Intercomparison Study: Iodine
Exper. Rng anal
Res. 3 Sigma (R + SR)
- , . - ?.- ''-'-','
41.0 2.89 0.492
51.0 2.52 0.492
^ft -ffc ' ' ' "1 fi€t f 1*1 4fi'3t
fJfc+V^ ' A-rVv \M&*
54.0 1.00 0.197
f
44.0 0.58 0.098
52.0 2.52 0.492
51.0 2.08 0.394
21.0 2.52 0.492
fftd -
-------
EMSL-LV Intel-comparison Study: Iodine in Water, 7-Aug-1902
Iodine-131
6/7
Data sorted by Laboratory Average
Average
42.67
43.00
43.00
43.00
43.00
43.00
43.33
43.33
43.67
43.67
43.67
43.67
43.67
44.00
44.00
44.00
44.00
44.00
44.33
44.33
44.33
44.33
44.67
44.67
44.67
45.00
45.00
45.00
45.00
45.00
Tag Lab
AY
OB
O
GE
DL
BL
CJ
BO
X
R
NJ
L
AF
SF
LF
JR
FU
AP
Q
MP
M
A
PV
E
DY
1C
DD
D
C
BM
Average Tag
45.00
45.00
45.33
45.33
45.33
45.33
45.33
45.67
45.67
45.67
46.00
46.00
46.00
46.00
46.33
46.33
46.33
46.67
47.00
47.00
47.00
47.67
47.67
47.67
48.00
48.00
48.33
48.33
48.33
48.33
Lab
AU
AK
U
S
I
HK
EX
ME
J
DT
OA
ML
IU
AJ
Z
KL
EH
SS
JS
EB
CA
Y
HJ
FL
PB
EL
TR
QK
MQ
CQ
Average Tag
48.33
48.67
48.67
49.00
49.33
50.00
50.00
50.00
50.33
50.67
50.67
50.67
51.33
51.67
51.67
51.67
52.33
53.00
53.00
56.00 ft
56.67 ft
62.00 x
62.33 x
63.33 x
66.00 x
66.00 x
72.00 x
86.00 x
270.00 x
552.33 x
Lab
AN
TI
BH
DM
BW
SW
MS
AI
CP
DG
CE
AZ
DR
RM
RC
LR
GI
SZ
QX
BC
TL
NH
AA
OT
PU
AW
QU
RQ
FE
K
% Frequency distribution of responding labs(expected prec. vs known value)
IU* - - - - -
-6
• s No data
.
la||
known
value
submitted TAG SYMBOLS
0 s Insufficient data x = Determined to be an
•
*2 exp. prec. +4
ft s Above control
outlier & = Below control
•1
+6
limit
limit
-------
7/7 EMSL-LV Intel-comparison Study: Iodine in Water, 7-Aug-1992
Iodine-131
% Frequency distribution of responding labsCstd. dev. vs mean value)
10-
•* "4 std. dev. -2 ^^ +2 std. dev. +< +*
value
------- |