# The Figge-Fencl Quantitative Physicochemical Model

of Human Acid-Base Physiology (Version 3.0)

by James J. Figge, MD, MBA, FACP

##### Copyright 2003 - 2013 James J. Figge.

Published 8 October, 2012; updated on 28 April, 2013;
updated on 27 October, 2013;

on *www.Figge-Fencl.org* and *www.acid-base.org*.

# Statistical Validation of the Figge-Fencl Quantitative
Physicochemical Model

(Version 3.0)

**Figure 1. pH of albumin-containing solutions as calculated by the
Figge-Fencl quantitative physicochemical model (version 3.0) (y-axis), versus
measured pH (x-axis). Experimental data cover the pH range of 6.85 to 7.94. Experimental
data (n = 65) are from Figge, Rossing and Fencl, ***J Lab Clin Med. *1991; 117: 453-467.
The slope of the regression line is 1.0068 (98% confidence limits: 0.9672 to 1.0464). Thus,
the slope is not significantly different than 1.0000. The intercept is -0.0469.

R = 0.99157, and R^{2} = 0.9832.

Paired *t* Test.

The mean difference, { Σ(calculated pH - measured pH) } / 65 = 0.0034 (+/- 0.0329 Standard Deviation).

The 98% confidence interval for the mean difference is calculated using: *t* (n-1, alpha/2) = 2.386; where n = 65; alpha=0.02.

The 98% confidence interval for the mean difference is 0.0034 +/- (2.386)(0.0329)/SQRT(65) = 0.0034 +/- 0.0097.

Hence, the mean difference is not statistically different than zero.