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I have a query. In different places I had the experience of reporting
the stability in different ways. In both ways 6 replicate samples were
processed and analysed both for the test and reference samples.
1st method involved taking Peak response into criteria (as peak area)
Correction Factor = Concentration of Comparison Stock / Concentration
of Stability Stock
Corrected Response = Stability Stock Response x Correction Factor
% Stability = Mean Corrected Response of Stability Stock / Mean
Response of Comparison Stock *100
In the second method: involved the use of peak area ratio.
Since there are 2 sets each with 6 samples, ANOVA test is performed
and the % stability is calculated at the 90% confidence interval. This
procedure involved taking into consideration the use of mean of PAR,
SD and %CV initially and then the values are log transformed for both
the test and reference sample set. the differences of the means is
then taken and the standard error of the difference was generated.
since we have equal set of samples in test and references the degrees
of freedom was chosen as 10. The 't' value for the equality of means
was then taken and the %stability reported as a mean of the lower and
upper limits of the 90% confidence intervals.
Which method is appropriate and why??
Waiting for expert comments.
Thanks and Regards,
Santosh Tata, BS (Pharm. Sci)
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