## Science vs. regulations [Regulatives / Guidelines]

Hi Achievwin,

» Then a priori in the protocol SAP include limitations on reporting AUCinf and %Extrp.
» 1. R2>0.800

Why this – arbitrary – number? Given, I have seen it in lots of SAPs.
$$\small{R^2}$$ (strongly!) depends on the number of time points $$n$$ (see this rather old thread). $$\small{R_{\textrm{adj}}^{2}}$$ is better though still not independent from $$n$$ (that’s a misconception sold by software vendors).
If clearance is variable and/or the analytical variability is high, a low correlation may be perfectly fine, whereas in the opposite case even 0.9 may indicate a poor fit. Unless you have data of a previous study with the same analytical method, IMHO, a pre-specified cut-off does not make sense.
Furthermore, never trust in results of a silicon-based life-form. Visual inspection of the fit is mandatory.

PS: 0.8 with three significant digits: 0.8005 is OK and 0.8004 not. Really?

Dif-tor heh smusma 🖖
Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮
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