Validation Statistical tools

The validation results shown in this specific example might lead one to make a generalized rule that the optimal complexity of a model corresponds to the level at which the RMSEP is at a minimum. However, it is not always the case that RMSEP-versus-complexity graph shows such a distinct minimum, and therefore such a generalized rule can result in overfit models. Alternatively, it might be more appropriate to choose the model complexity at which an increase in complexity does not significantly decrease the prediction error (RMSEP). This choice can be based on rough visual inspection of the prediction error-versus-complexity plot, or from statistical tools such as the/-test.50,51... 

Statistical tools for validation and evaluation of analytical methods... 

An automated parameterization may be difficult to set up. But when this has been accomplished, the process is substantially faster than the manual method, and much larger bodies of data can be fitted simultaneously. The main drawback of the automated scheme is that errors may remain undetected more easily than in manual parameterization. Automated parameterization therefore requires substantial validation to identify outliers in the data set and deficiencies in the force field. Statistical tools should be used to verify that each parameter is well defined by the chosen set of reference data, and any iU-fitting data points can be rationalized on sound physical grounds. 

Validation of assays can be made in the absence of a standard. The validation then relies on statistical tools such as cluster or mixture analysis. Assuming that a few sera of known status are available to establish the feasibility of the assay system, it is possible to obtain a rough estimate of the assay s performance characteristics. Then, several thousands of animals in the target population can be tested in the absence of known infection status data other than possibly scattered clinical observations. If a clear bimodal frequency distribution becomes evident with a large peak consisting of many animals at the low... 

Indeed, once the mathematical models are validated by classical statistical tools (e.gi, ANOVA, or analysis of the variance analysis of the lack of ht) (15). we can draw the response. surfaces representing t)ic evolution of the responses in the whole domain studied, when two factors are varying and the third one is fixed. From the different diagrams of isoresprmse curves, we can determine the influence of the different factors considered on the responses-... 

System suitability is guaranteed if both apparatus test and validation match their requirements. It is best performed on a routine basis and can be done very easily if the HPLC apparatus is equipped with a computer data system. Then during each run or in well-defined intervals a number of parameters are acquired plate number, resolution, precision, retention time, relative retention time (i.e. k value) and peak asymmetry-also if necessary linearity and limits of quantification. The results are followed by statistical tools, including easy-to-monitor graphical documentation with control charts. ... 

Acceptance criteria should take into account method performance attributes and the intended use of the methods. For example, in some instances it may be critical that the method precision and sensitivity (i.e., for impurities) are similar to that obtained by the method development laboratory. In such cases, the samples selected for transfer purposes, the statistical tools applied to demonstrate equivalence and the acceptance criteria should be selected carefully to ensure that the method performance is properly evaluated. On the other hand, in some instances the capabilities (e.g., sensitivity) of the development method may exceed the method performance requirements for commercial release testing. For example, while a gas chromatographic (GC) method may be validated to have sensitivity down to 0.002% for a number of residual solvents monitored during development and, if the specifications are set only on total residual solvents with a limit of 0.5%, it may not be necessary to demonstrate sensitivity for individual solvents to 0.002% to qualify the QC laboratory for routine use. The acceptance criteria should be considered on a case-by-case basis for each method for each product and must be established in advance of the formal testing. 

What is the practical value of a questionnaire or survey This can be assessed with a variety of research methods and statistical tools. Many are beyond the scope of this text, but a few basic concepts are pertinent. First, questionnaires to measure person factors can be reliable, tiiough not valid. To be valid, they must be reliable. A reliable survey gives consistent results. You assess this by comparing answers across different survey items that supposedly measure the same factor or by comparing two different administrations of the same survey. 

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