A near-optimal heuristic for the sequencing problem in multiple-batch flow-shops with small equal sublots

In this paper, we consider the lot-streaming problem of sequencing a set of batches, to be processed in equal sublots, in a flow-shop, so as to minimize makespan. A new heuristic procedure, called the bottleneck minimal idleness heuristic, is developed. Results of an experimental study are presented. It is shown that the proposed procedure generates solutions that are very close to the optimal solutions, and that the solutions generated are better than those obtained by using the fast insertion heuristic, considered to be a good heuristic for solving the flow-shop scheduling problem, when applied to the problem on hand.     

On regression method for estimating a population proportion

In this paper the regression method of estimation has been discussed for the estimation of proportion of the units possessing the given characteristic. An unbiased regression type estimator has also been discussed. An unbiased estimator is given for estimating the common MSE/variance of the estimators discussed. The results have also been extended to deal with the populations of a peculiar nature.     

Detection of influential observations in multivariate regression

Several methods have been suggested, in the literature, to detect influential observations from the data fitting usual linear model y=X???+???, ???∽N(0, ???2I). Recently, Chatterjee & Hadi (1986) have reviewed most of these available methods and described the inter-relationships between them. In this article, we extend some of these methods to the case of multivariate regression data. We consider several data sets to illustrate the methods.     

Statistical tests for random effects in staggered nested designs

In this paper, we present certain statistical tests under a staggered nested design set-up, for the hypotheses that certain variance components are zero. To do so, the particular variance-covariance, structure induced by the staggering is exploited and certain results of multivariate analysis are used. In most problems, the test statistics can be easily computed. An example is provided for illustration and some power computations for comparison of test statistics are shown.     

A new jackknife test for homogeneity of variances

A new jackknife test is proposed to test the equality of variances in several populations. The new test is based on jackknifing one group of observations at a time, instead of one observation in each group as recommended by Miller for a two sample case, and by Layard for several samples. The proposed test is examined, and compared with other tests, in terms of power and robustness with respect to a wide variety of non-normal distributions. It is found that the new test is robust and has reasonably high power for normal as well as for non-normal observations, irrespective of the sample size. Furthermore, the proposed test is certainly superior to all other tests considered here in small to moderate size samples, and is as good as or better than the other tests in large samples, irrespective of the distribution of sampling observations.     

On the q-Weibull Distribution and Its Applications

The q-Weibull distribution is a stretched model for Weibull distribution, obtained by introducing a new pathway parameter q, which facilitates a slow transition to the Weibull as q → 1. In this article, we make a detailed study of the properties of the q-Weibull distribution and we apply it to a data on cancer remission times for which this distribution is a better fit than Weibull. Results relating to reliability properties, estimation of parameters, and applications in stress-strength analysis are also obtained.     

Detection of outliers in bivariate time series data

In this article, we use the influence function matrix of auto and cross-correlations of a bivariate (multivariate) time series for detecting the outliers. The multivariate analog of the graphical method of Chernick et. al. (1982), to detect outliers and partial outliers is presented. A simulation study illustrating the method is also given.