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Dear All,
Here is a statistical question I need help to respond: Five batches of
tablets have been produced and the average drug content (10 tablets
assayed per batch) is 99.2 mg with a standard deviation of 2.4. How many
tablets should be assayed (sample size?) in order to statistically show
that there is zero or near zero possibility that an individual tablet
produced will have a drug content higher than 110 mg? Thank you.
Konstantinos Avgoustakis
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The following message was posted to: PharmPK
Dear Konstantinos,
You have 4.5 standard deviation [=(110-99.2)/2.4].
Assuming a normality distribution, the probability of being lower or equal to
110 is 0.999996602.
You may want to do an ANOVA to include the variability between batch to be more
precise.
You already have a sample size of 50 (10 tablet per batch), increasing the
sample size will just increase the power (more precise mean and variability of
the "true" distribution), it will not change the probability of having an
individual tablet above 110 mg.
Other non-parametric estimation is to calculate the proportion of individual
tablet that are above 110 mg in a very large sample size.
Jean
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Dear Avgoustakis,
Please check you want to study according USP or B.P. and the follow that book details.
Dr Zafar
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