Brownlee

This sum, when divided by the number of data points minus the number of degrees of freedom, approximates the overall variance of errors. It is a measure of the overall fit of the equation to the data. Thus, two different models with the same number of adjustable parameters yield different values for this variance when fit to the same data with the same estimated standard errors in the measured variables. Similarly, the same model, fit to different sets of data, yields different values for the overall variance. The differences in these variances are the basis for many standard statistical tests for model and data comparison. Such statistical tests are discussed in detail by Crow et al. (1960) and Brownlee (1965). 

Brownlee, K. A., "Statistical Theory and Methodology in Science and Engineering," 2nd ed., John Wiley and Sons, New York (1965). ... 

J. Hine, Physical Organic Chemistry, McGraw-Hill, New York, 1962, pp. 95-98 P. R. Wells, Linear Free Energy Relationships, Academic Press, New York, 1968, pp. 35-44 M. Charton, Prog. Phys. Org. Chem. 10 81 (1973) S. Ehrenson, R. T. C. Brownlee, and R. W. Taft, Prog. Phys. Org. Chem. 10 1 (1973). 

For commercial Ephedra the British Pharmaceutical Codex, 1934, specifies a total alkaloidal content of not less than 1-25 per cent, when assayed by the method therein prescribed. The proportion of Z-ephedrine is generally about 70 per cent. Methods of assay for total alkaloids are described by Feng and Read and by Krishna and Chose, who discuss the various difficulties involved and comments on these and other methods have been made by various workers. Conditions affecting the results of such assays have also been discussed by T ang and Wang, and Brownlee has shown that chloroform is not a suitable medium for the assay since it converts ephedrine quickly and 0-ephedrine slowly to the hydrochloride. 

TABLE 8. [Pg.510]

Donald E. Brownlee, Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580, USA Stephen J. Burges, Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, USA... 

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