Validation of Regression Models: Methods and Examples

Snee, Ronald D.

doi:10.2307/1267881

Cited by 425 publications

(393 citation statements)

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“…Prior to model development, the dataset was split into training and test sets using the 'Venetian blinds' method [25] according to total acidity (TA). The training set S 0 and the test set S 1 had the same TA distribution (y 0 and y 1 ), each containing 186 and 185 samples, respectively.…”

Section: Model Performance Evaluationmentioning

confidence: 99%

Application of LS-SVM to non-linear phenomena in NIR spectroscopy: development of a robust and portable sensor for acidity prediction in grapes

Chauchard¹,

Cogdill²,

Roussel³

et al. 2004

Chemometrics and Intelligent Laboratory Systems

350

250

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Nowadays, near infrared (NIR)technology is being transferred from the laboratory to the industrial world for on-line and portable applications. As a result, new issues are arising, such as the need for increased robustness, or the ability to compensate for non-linearities in the calibration or instrument. Semi-parametric modeling has been suggested as a means for adapting to these complications. In this article, Least-Squared Support Vector Machine (LS-SVM) regression, a semi-parametric modeling technique, is used to predict the acidity of three different grape varieties using NIR spectra. The performance and robustness of LS-SVM regression are compared to Partial Least Square Regression (PLSR) and Multivariate Linear Regression (MLR). LS-SVM regression produces more accurate prediction. However SNV pretreatment is required to improve the model robustness.NIR Spectroscopy Robust calibration LS-SVM PLSR MLR Grapes tartaric and malic acidity.

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Section: Model Performance Evaluationmentioning

confidence: 99%

Application of LS-SVM to non-linear phenomena in NIR spectroscopy: development of a robust and portable sensor for acidity prediction in grapes

Chauchard¹,

Cogdill²,

Roussel³

et al. 2004

Chemometrics and Intelligent Laboratory Systems

350

250

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“…The PRESS procedure was used for crossvalidation (Weisberg, 1985;Fritts et al, 1990;Meko, 1997;Touchan et al, 1999). Model stability was also verified using a split-sample procedure (Snee, 1977;Meko and Graybill, 1995) that divided the full period into two subsets of equal length (1931-64 and 1965-98).…”

Section: Dendroclimatic Reconstructionmentioning

confidence: 99%

Preliminary reconstructions of spring precipitation in southwestern Turkey from tree‐ring width

Touchan

Garfin

Meko

et al. 2003

Intl Journal of Climatology

131

101

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Two reconstructions of spring (May-June) precipitation have been developed for southwestern Turkey. The first reconstruction (1776-1998) was developed from principal components of nine chronologies of Cedrus libani, Juniperus excelsa, Pinus brutia, and Pinus nigra. The second reconstruction (1339-1998) was derived from principal components of three J. excelsa chronologies. Calibration and verification statistics of both reconstructions indicate reasonably accurate reconstruction of spring precipitation for southwestern Turkey, and show clear evidence of multi-year to decadal variations in spring precipitation. The longest period of reconstructed spring drought, defined as consecutive years with less than 80% of normal May-June precipitation, was 4 years (1476-79). Only one drought event of this duration has occurred during the last six centuries. Monte Carlo analysis indicates a less than 33% probability that southwestern Turkey has experienced spring drought longer than 5 years in the past 660 years. Apart from the 1476-79 extended dry period, spring droughts of 3 years in length have only occurred from 1700 to the present. The longest reconstructed wet period, defined as consecutive years with more than 120% of normal May-June precipitation, was 4 years (1532-35). The absence of extended spring drought during the 16th and 17th centuries and the occurrence of extended wet spring periods during these centuries suggest a possible regime shift in climate. Preliminary analysis of links between large-scale climatic variation and these climate reconstructions shows that there is a relationship between extremes in spring precipitation and anomalous atmospheric circulation in the region.

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“…There are a number of internal validation techniques that can be used within the same population, namely split sample [13] and cross validation methods [14]. These methods are not as rigorous as prospective studies by an independent investigation at another institution because of uncontrollable biases due to patient selection or data collection.…”

Section: Methodological Rigourmentioning

confidence: 99%

Severity of illness scoring systems and performance appraisal

Ridley¹

1998

Anaesthesia

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SummaryA large number of severity of illness scoring systems have been developed and they are widely used in intensive care practice. However, they are complex systems with their basis in mathematics. To use such systems effectively, it is important to appreciate what factors influence their performance so that they can be compared fairly and used most appropriately. The purpose of this review is to describe the methods commonly used to assess the various facets of performance in severity of illness scoring systems. The performance of the most frequently used scoring systems in adult intensive care practice are presented. The shortfalls, misuse and strengths of scoring systems are also discussed.Keywords Intensive care; severity of illness scoring systems. Severity of illness scores stratify critically ill patients, provide meaningful information in many clinical contexts and collate clinical practice. Generally, severity of illness scores measure the degree of illness and reflect the complexity of the disease process. However, such systems have had their use extended so that they may be used to predict and compare outcomes, allocate resources and examine the process of care. There is little doubt that severity scoring systems have revolutionised intensive care. However, their limitations include a failure to predict functional status or quality of life after critical illness.As with any tool or model, it is important that the correct severity scoring system is selected and then applied in the way its developers intended. Therefore, the purpose of this review is to analyse critically the development and performance of commonly employed intensive care severity of illness scores. The commonly used general adult severity of illness scores, measuring severity of illness at a fixed point and over time, will be described. Finally, their limitations and misuse will be briefly presented. AppraisalThe critical appraisal of the development of a severity of illness score involves the measurement of accuracy (calibration and discrimination), reliability, content validity and methodological rigour. Accuracy -calibrationCalibration refers to how closely the estimated probabilities of mortality generated by the severity scoring system correlate with actual mortality over the entire range of probabilities. In other words, this is the accuracy of measurement for every interval of measurement. Calibration is usually tested with a 'goodness of fit' test, where a large 'p' value is sought, suggesting that patients predicted to die and those who actually die come from the 1185ᮊ 1998 Blackwell Science Ltd same population. One such goodness of fit test is the Hosmer-Lemeshow C statistic [6] and an example of the results is shown in Table 1.The Hosmer-Lemeshow goodness of fit C statistic compares the observed and expected frequencies over the entire range of deciles of risk from low to high and expresses the likelihood of the distributions being different using the Chi-squared statistic. In the example given, the p value is 0.591, sug...

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Validation of Regression Models: Methods and Examples

Cited by 425 publications

References 0 publications

Application of LS-SVM to non-linear phenomena in NIR spectroscopy: development of a robust and portable sensor for acidity prediction in grapes

Application of LS-SVM to non-linear phenomena in NIR spectroscopy: development of a robust and portable sensor for acidity prediction in grapes

Preliminary reconstructions of spring precipitation in southwestern Turkey from tree‐ring width

Severity of illness scoring systems and performance appraisal

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