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The DOI matches its Crossref record; 22 of the 22 references it cites were found in a registry or an index.

External Validation and Prediction Employing the Predictive Squared Correlation Coefficient — Test Set Activity Mean vs Training Set Activity Mean

Schüürmann, Gerrit, Ebert, Ralf-Uwe, Chen, Jingwen, Wang, Bin, Kühne, Ralph·2008·Journal of Chemical Information and Modeling

Abstract

The external prediction capability of quantitative structure-activity relationship (QSAR) models is often quantified using the predictive squared correlation coefficient, q (2). This index relates the predictive residual sum of squares, PRESS, to the activity sum of squares, SS, without postprocessing of the model output, the latter of which is automatically done when calculating the conventional squared correlation coefficient, r (2). According to the current OECD guidelines, q (2) for external validation should be calculated with SS referring to the training set activity mean. Our present findings including a mathematical proof demonstrate that this approach yields a systematic overestimation of the prediction capability that is triggered by the difference between the training and test set activity means. Example calculations with three regression models and data sets taken from literature show further that for external test sets, q (2) based on the training set activity mean may become even larger than r (2). As a consequence, we suggest to always use the test set activity mean when quantifying the external prediction capability through q (2) and to revise the respective OECD guidance document accordingly. The discussion includes a comparison between r (2) and q (2) value ranges and the q (2) statistics for cross-validation.

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Metadata

Authors
Schüürmann, G., Ebert, R.-U., Chen, J., Wang, B., & Kühne, R.
Venue
Journal of Chemical Information and Modeling
Published
2008-10-28
Volume
48
Issue
11
Pages
2140-2145
ISSN
  • 1549-9596 (ISSN-L)
  • 1549-960X
OpenAlex
W2073150707
Cited by
531
References
22
FWCI
21.77
Type
journal article
Language
en
Open access
closed

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