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2 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures • H24.03
additions of 34.57 g/L thiosulfate ion and 5.444 g/L
sodium sulfite were made to that “seasoned” sample.
POTENTIOMETRIC TITRATION STATISTICS
Repeatability Standard Deviation, 1s
r
& 95 Percent
Confidence Estimate (not including bias)
Repeatability standard deviation is an estimate of the
variability one trained analyst should be able to obtain under
favorable conditions (analyzing a sample, with one
instrument, within one day).
The 95 percent confidence estimate (calculated using the
repeatability standard deviation) around a single test will
include the mean value 95 percent of the time.
Bias
Bias is a statistically significant deviation of the mean from
the known mix level at a 95 percent confidence level. It is
determined for “fresh” samples only. Bias is not determined
for “seasoned” samples, since the component concentration
level was not determined independently of the test method.
A statistically significant bias for thiosulfate of
(-1.09 percent) was found for a “fresh” tank Process ECN-2
Fixer sample. The biases for Hypo Index and Sodium Sulfite
were not statistically significant. However, the bias for
thiosulfate was judged not to be practically significant.
HYPO INDEX (1 mL)
Samples
(Process ECN-2 Fixer)
Mean Level
(mL 0.1 N I
2
)
(N)
Repeatability
Standard Deviation, 1S
r
(mL 0.1 N I
2
)
95 Percent
Confidence Estimate
(mL 0.1 N I
2
)
“Fresh” at “Aim” 10.02 5 0.086 ± 0.24
“Seasoned”, As
Received
15.80 5 0.073 ± 0.20
“Seasoned” with
Standard Addition
19.38 5 0.14 ± 0.39
THIOSULFATE
Samples
(Process ECN-2 Fixer)
Mean Level
(g/L S
2
O
3
=
)
(N)
Repeatability
Standard Deviation, 1S
r
(g/L S
2
O
3
=
)
95 Percent
Confidence Estimate
(g/L S
2
O
3
=
)
“Fresh” at “Aim” 81.18 5 0.67 ± 1.9
“Seasoned”, As
Received
125.67 5 0.47 ± 1.3
“Seasoned” with
Standard Addition
153.79 5 0.60 ± 1.7
SULFITE
Samples
(Process ECN-2 Fixer)
Mean Level
(g/L Na
2
SO
3
)
(N)
Repeatability
Standard Deviation, 1S
r
(g/L Na
2
SO
3
)
95 Percent
Confidence Estimate
(g/L Na
2
SO
3
)
“Fresh” at “Aim” 17.55 5 0.69 ± 1.9
“Seasoned”, As
Received
28.92 5 0.65 ± 1.8
“Seasoned” with
Standard Addition
35.69 5 1.18 ± 3.3