ABSTRACT
Ruggedness Test (RT) experiments were performed to assess the significance of the various main factors which affect pH measurements in low ionic strength aqueous solutions, as well as to establish the presence of interactions between the main factors. Stirring has an adverse effect on the measurement of pH, since it not only increases the random noise but also biases the measured value. Temperature control to the nearest 0.5 °C is sufficient for maintaining measurements accurate to 0.01 pH. Addition of NaNO3 or KCl can not be tolerated in accurate pH measurements. Three small two-factor interactions were also revealed.
ABSTRACT
A straightforward explanation of the statistical technique of ruggedness testing is presented. Efficient Plackett-Burman designs are used in ruggedness tests. These designs involve the simultaneous change of levels of a number of variables. The designs allow the ruggedness test user to determine the effect of the separated variables on the measurement process. This paper (Part I) deals with the common situation where two-factor and higher order interactions can be safely ignored. A method is presented for evaluating the experimental uncertainties. A detailed example of glass electrode measurements of pH of dilute HCl solutions is used to illustrate ruggedness testing procedures.
ABSTRACT
This paper is a continuation of the preceding article which introduced the reader to the general concepts of ruggedness testing. The current paper describes the effects of interactions on the measurement process, and presents procedures for the separation of the main effects from the two-factor interactions. The general characteristics of interactions are described in some detail. A short-cut procedure is presented for the calculations. A number of examples of glass electrode measurements of pH of dilute acid solutions are used to illustrate ruggedness testing procedures.
