Ruggedness Plackett-Burman designs

ASTM El 169-89 Standard Guide for Conducting Ruggedness Tests (Plackett-Burman Design), American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959. 

Vander Heyden, Y., Hartmann, C., Massart, D. L., Michel, L., Kiechle, P., and Ernl, R (1995). Ruggedness tests for a high-performance liquid chromatographic assay comparison of an evaluation at two and three levels by using two-level Plackett-Burman designs. Anal. Chim. Acta 316, 15-26. 

To test the factors at three levels in a ruggedness test one usually applies the so-called reflected designs [17,19,23]. A reflected design is in fact a two level Plackett-Burman, full or fractional factorial design that is executed twice. Once the design contains the first extreme and the nominal level and once the other extreme and the nominal level. Both designs have one experiment in common, namely an experiment in which all factors are at nominal conditions. A reflected Plackett-Burman design for 7 factors is shown in Table 3.18. 

These two case studies are good examples of ruggedness tests that focus on the type of data analysis described in Section 3.4.6 and where one prefers not to carry out a statistical analysis. They will be described in detail later in this book (Chapter 5). The factors are examined at three levels in reflected Plackett-Burman designs. From the results of the designs normalized effects, Ex(%), are calculated. No statistical... 

A number of software packages or expert systems for ruggedness testing has been developed. RES (commercialized under the name Shaiker ) is an expert system created by Van Leeuwen et al. [4,23] and has been validated and evaluated [42,43]. It uses fractional factorial and Plackett-Burman designs and allows to test the factors at two or three levels. The interpretation criteria used here are the predefined values (see Section 3.4.8). 

This study was carried out with the intention of not only determining the ruggedness of the method but also to investigate the effect of confounding in the Plackett-Burman designs [26]. 

Three-level fractional factorial designs are also very useful, and charting the effects can be very helpful especially where there are more than three factors. The Plackett-Burman designs are often used to confirm (or otherwise ) the robustness of a method from the set value. Figure 17 shows some results from a ruggedness study for an HPLC method for salbutamol where the resolution factor, between it and its main degradation product is critical. 

The effect of each variable in the ruggedness test is determined by the difference between the average high and low levels, as is done in the Plackett-Burman design. However, the Youden technique, as modified by Steiner, differs from the Plackett-Burman technique in that the Youden-Steiner experiment is performed in duplicate, and the standard error is estimated differently. An estimate of the experimental error is calculated by equation 5. ... 

Ruggedness the capacity of an analytical method to remain unaffected and produce accurate data in spite of small but deliberately introduced changes in experimental conditions. Fractional factorial or Plackett Burman designs are frequently used to screen the impact of those changes. 

The ruggedness of a method can be tested using two types of experimental designs. Procedure related factors at the one hand are examined mainly in screening designs of the Plackett-Burman or... 

The ruggedization of the analytical procedure was performed by applying statistical screening techniques to minimize the effort required and, therefore, reduce the time and the cost substantially. The statistical approaches used in this study were those first introduced by Plackett-Burman (3.) and Youden-Steiner (4). Both techniques reduce the required effort since they use balanced incomplete block design experiments which can clearly indicate the non-affecting parameters from those that may have an effect. In this study the important variables of the analytical method were identified by using the Plackett-Burman technique. 

Table 3 Plackett-Burman Ruggedness Test Design for Seven Factors (A to G)...

An approach similar to that of Plackett and Burman called "Ruggedization" was introduced by Youden (4) for the screening of only seven variables with eight experiments. The combination of the high and low levels of the variables in Youden s design is... 

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