In the common linear and quadratic regression model with an autoregressive error structure exact D-optimal designs for weighted least squares analysis are determined. It is demonstrated that for highly correlated observations the D-optimal design is close to the equally spaced design. Moreover,...

We consider the triangle test with replications, i.e. each assessor is asked repeatedly. A commonly used test statistic for this situation is the sum of all correct assessments, summed over all assessors. Several authors (e.g. o’Mahony, 1982, Brockhoff and Schlich, 1998) argue that the...

In this paper we examine two widely used methods to obtain a transformation in Taguchi experiments, namely the lambda plot and the beta technique. We consider different situations with contrasts influencing the mean and / or the variance of the response. Our simulation study reveals that the...

We consider a model for sensory profiling data including translation, rotation and scaling. We compare two methods to calculate an overall consensus from several data matrices: GPA and STATIS. These methods are briefly illustrated and explained under our model. A series of simulations to compare...

If the number of assessors in a difference test is not large enough to ensure the desired power of the testing procedure, then it is often advised to use assessors repeatedly. That is, each assessor performs the testing not just once but several times. There is a discussion going on, how results...

A statistical method for analysing sensory profiling data obtained by means of fixed vocabulary or free choice profiling is discussed. The most interesting feature of this method is that it involves only simple statistical treatment and can therefore be performed using standard software...

This paper generalizes Kushner's (1997) method for finding optimal repeated measurements designs to optimal designs under an interference model. The model we assume is for a onedimensional layout without guard plots and with different left and right neighbour effects. The resulting optimal...

This paper discusses whether differences in the data structure of observational and experimental studies should lead to different strategies for variable selection. On the one hand, it is argued that outliers in the predictor variables have to be treated differently in the two kinds of studies....

The so-called good-laboratory-practice (GLP) test provides an experimental design and appropriate statistical analysis for the problem of analyst performance assessment in microbiological laboratories. For a given sample material multiple dilution series are generated yielding colony counts from...