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SEMI C1-0705 © SEMI 1978, 2005 10 Table 5 Data Reporting – Exampl e 6.1.7 Sample A (0.19 + 0.21 + 0.25 + 0.15 + 0.23) / 5 = 0.206 Sample B (0.31 + 0.21 + 0.17 + 0.22 + 0 . 26) / 5 = 0.234 Average (0.206 + 0.234) / 2 = 0.…
SEMI C1-0705 © SEMI 1978, 2005 9
90% Upper Confidence
Limit
n
s
t
p
df 10.0,
UCL%90
where n is the total number of assay measurements taken on the
sample in question and t is a t-statistic with the associated degrees of
freedom and 10% of the distribution to its right
6.1.4.2 In cases for trace metals, trace anions, and moisture where more samples are measured, statistical quantities
analogous to those in Table 2 should be constructed. For methods where automatic consecutive measurements can
be obtained from the instrument, Results A, B, C, and D should be the mean of five or more instrumental
measurements.
6.1.5 Summary of Criteria for Success — The success of the criteria for each figure of merit depends on the
specification, the matrix of the analyte, and levels of detection required. For trace metals, trace anions and moisture,
method success criteria are found in Table 4. For assays the 90% upper confidence limit can not exceed 30% of the
specification’s width.
Table 4 Method Success Criteria for Trace Metals, Trace Anions and Moisture
Figure of Merit Criteria for Successful Method
Accuracy
Spiked Recovery Study
75-125% Spiked Recovery for each spiked sample.
Method Precision
Spiked Recovery Study
% Recovery Range less than or equal to 35%.
Measurement Precision Maximum RSD = 20% of the concentration of each spiked
sample where:
100x
Sample Spiked of Conc.
ResultStd.Dev.
RSD
Method Detection Limit As per SEMI C10: Guide for Determination of Method
Detection Limits; Method Detection Limits cannot exceed the
specification.
Interference Checks
If interferences were examined or potential interferences
exist, list them.
6.1.6 Applicability to Existing Specifications — The current implementation of Method Validation only applies to
new or revised specifications. Any prior method validated by SEMI to support a given specification still remains
applicable to that specification.
6.1.7 Example: Trace Metals, Trace Anions and Moisture — Suppose that repeat measurements from four samples;
A, B, C and D were available as follows:
Sample A: 0.19, 0.21, 0.25, 0.15, 0.23
Sample B: 0.31, 0.21, 0.17, 0.22, 0.26
Spiked Sample C: 0.83, 0.62, 0.76, 0.79, 0.80
Spiked Sample D: 0.77, 0.87, 0.69, 0.83, 0.84
NOTE 2: Table 5 illustrates the calculations required as per Table 2.
SEMI C1-0705 © SEMI 1978, 2005 10
Table 5 Data Reporting – Example 6.1.7
Sample A (0.19 + 0.21 + 0.25 + 0.15 + 0.23) / 5
= 0.206
Sample B (0.31 + 0.21 + 0.17 + 0.22 + 0.26) / 5
= 0.234
Average (0.206 + 0.234) / 2 = 0.220
Spike The spike level is to be ½ the relevant specification. If the
specification is 1 ppb, then the spike would be 0.5 ppb.
Spike Sample C (0.83+0.62+0.76+0.79+0.80) / 5
= 0.760
Spike Sample D (0.77+0.87+0.69+0.83+0.84) / 5
= 0.800
Recovery 1 (0.760 – 0.220) = 0.540
% Recovery 1 (0.540 / 0.5) = 108
Recovery 2 (0.800 – 0.220) = 0.580
% Recovery 2 (0.580 / 0.5) = 116
Average % Recovery (108 + 116) / 2 = 112
% Recovery Range (116 – 108) = 8
Result Standard Deviation Since repeat measurements were available in this example, report
the sample standard deviations.
Sample A: 0.038
Sample B: 0.053
Sample C: 0.082
Sample D: 0.071
Relative Standard Deviation
(as a %)
Since repeat measurements were available in this example, report
the relative sample standard deviations.
Samp. A: 100 × (0.038 / 0.220) = 17.5
Samp. B: 100 × (0.053 / 0.220) = 24.2
Samp. C: 100 × (0.082 / 0.720) = 11.4
Samp. D: 100 × (0.071 / 0.720) = 9.9
Note use of the average of 0.220 and the sum of the average +
spike (0.720) above.
NOTE 3: This example provided the data for the first three success criteria found in Table 4 as well as providing other required
summary statistics. Table 6 summarizes performance relative to the success criteria.
Table 6 Method Success Criteria for Trace Metals, Trace Anions, and Moisture –
Example 6.1.7
Figure of Merit Criteria for Successful Method
Accuracy
Recovery 1 (108%) as well as Recovery 2 (116%) are in the
required 75–125% Spiked Recovery range.
Method Precision
The % Recovery Range was 8% and meets the requirement of not
exceeding 35%.
Measurement Precision The maximum RSD for the spiked recoveries is 11.4% which is
less than the maximum allowable 20%. Note that the RSDs
calculated for Samples A and B are not relevant for this
requirement.
SEMI C1-0705 © SEMI 1978, 2005 11
Figure of Merit Criteria for Successful Method
Method Detection Limit Not illustrated in this example, an example is provided with SEMI
C10. The Method Detection Limit must be less than or equal to
the specification.
Interference Checks
List as necessary.
6.1.8 Example: Assay With Stated Upper and Lower Specification Limits — Suppose that the liquid chemical in
question has a target specification of 28% with a lower specification limit of 27% and an upper specification limit of
29%. The specification width is 2% = 29% 27%. Suppose the following data was available all as percentages:
Historical Sample A: 28.9, 29.1, 29.9
Historical Sample B: 27.8, 27.6, 27.6, 27.7
Current Sample: 28.1
For purposes of calculating the degrees of freedom and the pooled standard deviation as per Table 7:
009.0 ,4 ,280.0 ,3
2
22
2
11
snsn
,
Where
2
22
1
29.9) 29.1, (28.9, dev. std. )52915.0(280.0 s
2
2
2
27.7) 27.6, 27.6, (27.8, dev. std. 009.0 s
The degrees of freedom = 5 = (3-1) + (4-1) exceeds the minimum requirement of 4 and the pooled standard
deviation is calculated as:
343.01174.0s
32
)009.0(3)280.0(2
1n
s1n
s
p
N
1i
i
N
1i
2
ii
p
The 90% UCL is calculated as: 506.0
1
343.0
476.1 UCL%90
10.0,
n
s
t
p
df
Where n = 1 = number of current meas. taken on sample and the t statistic is from Table 7. Since the 90% UCL /
spec. width = 0.506/2 = 25.3% < 30% method validation is established.
Table 7 t-statistics for Assay
Degrees of Freedom t-statistic
4 1.533
5 1.476
6 1.440
7 1.415
8 1.397
9 1.383
10 1.372
11 1.363
12 1.356