Youden

Youden, W. J., Statistical Manual of the AOAC, AOAC, 1111 North 19th St., Arlington, VA, 22209. 

A reagent blank corrects the measured signal for signals due to reagents other than the sample that are used in an analysis. The most common reagent blank is prepared by omitting the sample. When a simple reagent blank does not compensate for all constant sources of determinate error, other types of blanks, such as the total Youden blank, can be used. 

Youden, W. J. Statistical Techniques for Collaborative Tests in Statistical Manual of the Association ofOjficial Analytical Chemists. Association of Official Analytical Chemists Washington, D.C., 1975. 

W. J. Youden, Experimentation and Measurement (Publication 672), National Institute of Standards and Technology, Gaithersburg, Md., 1991. 

The example demonstrates that all relevant information must be used ignoring the fact that the PM and HPLC measurements for / = 1. .. 5 are paired results in a loss of information. The paired data should under all circumstances be plotted (Youden plot. Fig. 2.1, and Fig. 1.23) to avoid a pitfall it must be borne in mind that the paired r-test yields insights only for the particular (addi-... 

Analysis of variance (ANOVA) tests whether one group of subjects (e.g., batch, method, laboratory, etc.) differs from the population of subjects investigated (several batches of one product different methods for the same parameter several laboratories participating in a round-robin test to validate a method, for examples see Refs. 5, 9, 21, 30. Multiple measurements are necessary to establish a benchmark variability ( within-group ) typical for the type of subject. Whenever a difference significantly exceeds this benchmark, at least two populations of subjects are involved. A graphical analogue is the Youden plot (see Fig. 2.1). An additive model is assumed for ANOVA. 

At least two parameters are tested by the same laboratory on many nominally similar samples. In both cases, the simplest outcome is a round patch in the Youden plot, see Fig. 2.1, of points that signifies just noise, no correlation. .. no participating laboratory (or sample or point in time) is exceptional. On the other hand, an elliptical patch, especially if the slope deviates from what could be expected, shows that some effects are at work that need further investigation. After just noise, the... 

Youden WJ (1991) Experimentation and Measurement. NIST Special Publication 672, Reprint of 1961, U.S. Department of Commerce. 

The method developer should identify critical points in the method. Frequently, the Youden test may be used to determine if temperature, time, flow rate for solid-phase extraction, weight, volume, and other variables in the method are critical. The developer needs to identify if it is acceptable to take a break during a procedure, length of the break, and steps that need to be completed quickly. Because of differences in background and training between analysts, method developers should not assume that other analysts will perform a technique in the same way as in the developer s laboratory. Often analysts will have different interpretations of simple terms such as shake , slow , complete , and fast . 

Data analysis for this series was performed using MathCad and the statistical methods used are described in greater detail in Youden s monograph [7] and in Mark and Workman [8], We use the MathCad worksheets both to illustrate how the theoretical concepts can be put to actual use and also to demonstrate how to perform the calculations we describe. The worksheets will be printed along with the chapters in which they are first used. At a later date we are planning to enable you to go to the Spectroscopy home page (http //www.spectroscopymag.com) and find them. If, and when, the actual URLs for the worksheets become available, we will let you know. 

Part 4 Performing a ranking test to determine if either analytical method or location affects the results as a systematic error (bias) and Part 5 Computing the efficient comparison of two methods as described by Youden and Steiner in reference [7],... 

Figure 34-2 Simple experimental design for Youden/Steiner comparison of two Methods (data shown in Table 34-2).

Youden, W.J. and Steiner, E.H., Statistical Manual of theAOAC, 1st ed. (Association of Official Analytical Chemists, Washington, DC, 1975). 

Measuring Precision without Duplicates (Youden/Steiner) ... 

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