variability [General Sta­tis­tics]

posted by sinhmar – India, 2008-12-23 08:04 (5574 d 03:47 ago) – Posting: # 2961
Views: 21,106

❝ I need to understand better the differences between the terms:

❝ – CV% derived from calculation of mean and standard deviation of PK parameters

❝ – Intra and inter subject variability - derived from ANOVA analysis.


CV (coefficient of variation) is a constant used to define variability, based on standard deviation, in data without considering any effect. It is a statistical measure of dispersion of data points in data series around mean.
In crossover bioequivalence studies, ANOVA table divides the total variability into variability due to different effects like subject, sequence, period and treatment and residual variability is an undefined variability accounted to within subject variability and other nuisance effects. The intra-subject variability (within subject variability) reflects the residual variability after accounting for differences between subjects, periods, sequence and formulations.
And inter subject variability is a between subject variability calculated by taking out the residual effect (inter subject) from subject (Sequence) effect, as it is clear from the following formula:
Inter-subject CV = 100 x (MSSubject (Seq) - MSResidual/2)0.5

❝ Those two formulas provided in Canadian bioequivalence guidance can be applied using KINETICA software?


i don't have any idea about Kinetica... but we can calculate intra/inter CV in SPSS and SAS

❝ And is right when I calculate number of subjects using data about intra – subject variability, isn't it?


yes, we need intra CV for calculating number of subjects but for that we need ratio(T/R) of means also :-)


Edit: Standard quotes restored. [Helmut]

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