Communications in Statistics-simulation and Computation, 1997
A robust procedure is developed for testing the equality of means in the two sample normal model.... more A robust procedure is developed for testing the equality of means in the two sample normal model. This is based on the weighted likelihood estimators of Basu et al. (1993). When the normal model is true the tests proposed have the same asymptotic power as the two sample Student's t-statistic in the equal variance case. However, when the normality assumptions
Communications in Statistics-simulation and Computation, 1995
In this paper we consider a model based approach for estimating hierarchical kappa statistics to ... more In this paper we consider a model based approach for estimating hierarchical kappa statistics to demonstrate improved precision through modelling. An extensive simulation study shows the improvement over the classical estimates due to model smoothing in terms of reduced mean square error
Reconstitution of an in vitro system capable of DNA chain initiation in an eukaryotic system has ... more Reconstitution of an in vitro system capable of DNA chain initiation in an eukaryotic system has been attempted in several laboratories. They have previously reported the isolation of three distinct forms of DNA polymerase-..cap alpha.. from IMR-32 cells and 9-day-old embryonic chicken brains (9ECB). DNA primase activity is eluted from a DE-23 column with one of these Pol-..cap alpha..'s when a linear gradient is used. Irrespective of embryonic age, primase and a pol-..cap alpha.. activity coelutes at 250 mM K-POâ buffer. The complex containing Pol-..cap alpha../primase activities has been analyzed further on a continuous velocity gradient of either sucrose or glycerol. A polymerase-..cap alpha..-free primase activity sediments at 4.5S whereas the other 50% is recovered with the pol-..cap alpha.. activity which sediments at 11S. Compared to polydC and poly(dC dT), of the 9ECB primase catalyzed ³H-dXMP incorporation into polydT and M13 is very low. The template poly(dC, dT) is ...
We present a general approach based on chi-square goodness-of-fit tests for performing tests of s... more We present a general approach based on chi-square goodness-of-fit tests for performing tests of significance about the kappa statistic. We make recommendations for the particular goodness-of-fit test to use under different situations. We also compare the test statistics in terms of the generated confidence intervals about the kappa statistic.
Analogues of the likelihood ratio, Rao, and Wald tests are introduced in discrete parametric mode... more Analogues of the likelihood ratio, Rao, and Wald tests are introduced in discrete parametric models based on the family of penalized Hellinger distances. It is shown that the tests based on a particular member of this family provide attractive alternatives to the tests based on the ordinary Hellinger distance. These tests share the robustness of the Hellinger distance test, but are often closer to the likelihood-based tests at the model, especially in small samples. The convergence of ordinary Hellinger distance tests to limiting X 2 distributions are quite slow. The proposed tests are improvements in this respect.
Journal of the Royal Statistical Society: Series D (The Statistician), 1999
Hierarchical k-statistics are used to measure the extent to which two raters agree between themse... more Hierarchical k-statistics are used to measure the extent to which two raters agree between themselves when the rating scale is ordinal. If the agreement is not perfect, hierarchical kstatistics are useful to measure the agreement at several levels. In this paper a model-based method is proposed to estimate the hierarchical k. It has been noted before that the estimates obtained have smaller mean-squared error than the existing estimates in ®nite samples. In this paper we show that asymptotically also the model-based estimates are more precise in the sense of having smaller variances. Another advantage of the model-based method is that it can be extended easily to any weighting scheme and tables of any dimensions in both theory and practice.
Journal of the Royal Statistical Society: Series D (The Statistician), 2002
The Pearson's chi-square and the log likelihood ratio chi-square statistics are fundamental tools... more The Pearson's chi-square and the log likelihood ratio chi-square statistics are fundamental tools in goodnessof-fit testing. Cressie and Read (1984) constructed a general family of divergences which includes both statistics as special cases. This family is indexed by a single parameter, and divergences at either end of the scale are more powerful against alternatives of one type while being rather poor against the opposite type. Here we present several new goodness-of-fit testing procedures which have reasonably high power at both kinds of alternatives. Graphical studies illustrate the advantages of the new methods.
Communications in Statistics - Simulation and Computation, 1995
The minimum disparity estimators proposed by Lindsay (1994) for discrete models form an attractiv... more The minimum disparity estimators proposed by Lindsay (1994) for discrete models form an attractive subclass of minimum distance estimators which achieve their robustness without sacrificing first order efficiency at the model. Similarly, disparity test statistics are useful robust alternatives to the likelihood ratio test for testing of hypotheses in parametric models; they are asymptotically equivalent to the likelihood ratio test
Annals of the Institute of Statistical Mathematics, 2006
We fit parametric models to survival data in the case of censoring and (outlier) contamination. T... more We fit parametric models to survival data in the case of censoring and (outlier) contamination. To do so, we adapt the robust density power divergence methodology of Basu, Harris, Hjort, and Jones (Biometrika, 85, 549-559, 1998) to the case of censored survival data. Asymptotic properties, simulation performance and application to data are provided.
A multivariate analysis of 263 Mexican-American, African-American, and Non-Hispanic white non-ins... more A multivariate analysis of 263 Mexican-American, African-American, and Non-Hispanic white non-insulin-dependent diabetes mellitus patients with end-stage renal disease revealed that in subjects following a linear course of decline of renal function, Mexican-American ethnicity (p = 0.0503) and female sex (p = 0.0036) hasten the rate of decline of renal function, while age (p = 0.0004), hypertension duration (p = 0.0058), and diabetes duration (p = 0.0587) slow the rate of decline of renal function. Blood pressure and glycemic control do not predict the rate of decline. These data suggest that ethnicity and sex-related factors may be as important as blood pressure and glycemic control during the course of non-insulin-dependent diabetic nephropathy.
Communications in Statistics-simulation and Computation, 1997
A robust procedure is developed for testing the equality of means in the two sample normal model.... more A robust procedure is developed for testing the equality of means in the two sample normal model. This is based on the weighted likelihood estimators of Basu et al. (1993). When the normal model is true the tests proposed have the same asymptotic power as the two sample Student's t-statistic in the equal variance case. However, when the normality assumptions
Communications in Statistics-simulation and Computation, 1995
In this paper we consider a model based approach for estimating hierarchical kappa statistics to ... more In this paper we consider a model based approach for estimating hierarchical kappa statistics to demonstrate improved precision through modelling. An extensive simulation study shows the improvement over the classical estimates due to model smoothing in terms of reduced mean square error
Reconstitution of an in vitro system capable of DNA chain initiation in an eukaryotic system has ... more Reconstitution of an in vitro system capable of DNA chain initiation in an eukaryotic system has been attempted in several laboratories. They have previously reported the isolation of three distinct forms of DNA polymerase-..cap alpha.. from IMR-32 cells and 9-day-old embryonic chicken brains (9ECB). DNA primase activity is eluted from a DE-23 column with one of these Pol-..cap alpha..'s when a linear gradient is used. Irrespective of embryonic age, primase and a pol-..cap alpha.. activity coelutes at 250 mM K-POâ buffer. The complex containing Pol-..cap alpha../primase activities has been analyzed further on a continuous velocity gradient of either sucrose or glycerol. A polymerase-..cap alpha..-free primase activity sediments at 4.5S whereas the other 50% is recovered with the pol-..cap alpha.. activity which sediments at 11S. Compared to polydC and poly(dC dT), of the 9ECB primase catalyzed ³H-dXMP incorporation into polydT and M13 is very low. The template poly(dC, dT) is ...
We present a general approach based on chi-square goodness-of-fit tests for performing tests of s... more We present a general approach based on chi-square goodness-of-fit tests for performing tests of significance about the kappa statistic. We make recommendations for the particular goodness-of-fit test to use under different situations. We also compare the test statistics in terms of the generated confidence intervals about the kappa statistic.
Analogues of the likelihood ratio, Rao, and Wald tests are introduced in discrete parametric mode... more Analogues of the likelihood ratio, Rao, and Wald tests are introduced in discrete parametric models based on the family of penalized Hellinger distances. It is shown that the tests based on a particular member of this family provide attractive alternatives to the tests based on the ordinary Hellinger distance. These tests share the robustness of the Hellinger distance test, but are often closer to the likelihood-based tests at the model, especially in small samples. The convergence of ordinary Hellinger distance tests to limiting X 2 distributions are quite slow. The proposed tests are improvements in this respect.
Journal of the Royal Statistical Society: Series D (The Statistician), 1999
Hierarchical k-statistics are used to measure the extent to which two raters agree between themse... more Hierarchical k-statistics are used to measure the extent to which two raters agree between themselves when the rating scale is ordinal. If the agreement is not perfect, hierarchical kstatistics are useful to measure the agreement at several levels. In this paper a model-based method is proposed to estimate the hierarchical k. It has been noted before that the estimates obtained have smaller mean-squared error than the existing estimates in ®nite samples. In this paper we show that asymptotically also the model-based estimates are more precise in the sense of having smaller variances. Another advantage of the model-based method is that it can be extended easily to any weighting scheme and tables of any dimensions in both theory and practice.
Journal of the Royal Statistical Society: Series D (The Statistician), 2002
The Pearson's chi-square and the log likelihood ratio chi-square statistics are fundamental tools... more The Pearson's chi-square and the log likelihood ratio chi-square statistics are fundamental tools in goodnessof-fit testing. Cressie and Read (1984) constructed a general family of divergences which includes both statistics as special cases. This family is indexed by a single parameter, and divergences at either end of the scale are more powerful against alternatives of one type while being rather poor against the opposite type. Here we present several new goodness-of-fit testing procedures which have reasonably high power at both kinds of alternatives. Graphical studies illustrate the advantages of the new methods.
Communications in Statistics - Simulation and Computation, 1995
The minimum disparity estimators proposed by Lindsay (1994) for discrete models form an attractiv... more The minimum disparity estimators proposed by Lindsay (1994) for discrete models form an attractive subclass of minimum distance estimators which achieve their robustness without sacrificing first order efficiency at the model. Similarly, disparity test statistics are useful robust alternatives to the likelihood ratio test for testing of hypotheses in parametric models; they are asymptotically equivalent to the likelihood ratio test
Annals of the Institute of Statistical Mathematics, 2006
We fit parametric models to survival data in the case of censoring and (outlier) contamination. T... more We fit parametric models to survival data in the case of censoring and (outlier) contamination. To do so, we adapt the robust density power divergence methodology of Basu, Harris, Hjort, and Jones (Biometrika, 85, 549-559, 1998) to the case of censored survival data. Asymptotic properties, simulation performance and application to data are provided.
A multivariate analysis of 263 Mexican-American, African-American, and Non-Hispanic white non-ins... more A multivariate analysis of 263 Mexican-American, African-American, and Non-Hispanic white non-insulin-dependent diabetes mellitus patients with end-stage renal disease revealed that in subjects following a linear course of decline of renal function, Mexican-American ethnicity (p = 0.0503) and female sex (p = 0.0036) hasten the rate of decline of renal function, while age (p = 0.0004), hypertension duration (p = 0.0058), and diabetes duration (p = 0.0587) slow the rate of decline of renal function. Blood pressure and glycemic control do not predict the rate of decline. These data suggest that ethnicity and sex-related factors may be as important as blood pressure and glycemic control during the course of non-insulin-dependent diabetic nephropathy.
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Papers by Srabashi Basu