You Thought That This Would Be Easy? Seeking an Understanding of Episodic Volunteering

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - This article is intended as the leading article in a Special Issue of Voluntas devoted to episodic volunteering from a...     

Performance Evaluation of a Multi-state System Covering Imperfect Fault Coverage

Fault-tolerant networks are being used to provide more reliable network connections. Development of the fault-tolerant computing system requires accurate reliability modeling. Numerical formulations and complex models are commonly used for obtaining reliability measures. These measures are functions of component failure rates and fault-coverage. Coverage provides information about the fault and error detection, isolation, and system recovery capabilities. This research studied a system consisting three units in parallel with three types of failures namely, catastrophic, human, and unit failures incorporating the coverage factor and evaluated the various reliability measures of the considered multi-state system subject to imperfect fault coverage.     

Sustaining the Benefits of a Quality Initiative through Cooperative Values: A Longitudinal Study

Although research has shown that organizational cultural values influence the success of quality initiatives, how and when cultural values are influential is unclear. This longitudinal study asserts that quality management should be viewed from a dynamic perspective to better understand the role of cooperative cultural values in a quality initiative. We use a multilevel model of quality management, and develop time‐oriented hypotheses using a sociotechnical systems perspective to examine the role of cooperative values. Our analysis uses longitudinal data from over 30 U.S. federal government agencies, collected during an enterprise‐wide quality initiative. We find that, over time, the influence of organization‐level quality practices diminishes, but the influence of cooperative values increases; workgroup‐level quality practices remain consistently important. Our findings reveal the unexplored influences of cooperative values to sustain the benefits of quality management.     

A test for bivariate exponentiality against bifr alternative

A test is proposed for testing bivariate exponentiality against the Bivariate Increasing Failure Rate (BIFR) class of alternatives. The test statistic is a function of U-statistics and hence asymptotically normally distributed and consistent     

Estimation of the parameters of a truncated gamma distribution

This paper deals with the estimation of the parameters of a truncated gamma distribution over (0,τ), where τ is assumed to be a real number. We obtain a necessary and sufficient condition for the existence of the maximum likelihood estimator(MLE). The probability of nonexistence of MLE is observed to be positive. A simulation study indicates that the modified maximum likelihood estimator and the mixed estimator, which exist with probability one,are to be preferred over MLE. The bias, the mean square error, and the probability of nearness form a basis of our simulation study.     

A generalization of the log-series distribution

A new generalized logarithmic series distribution (GLSD) with two parameters is proposed.The proposed model is flexible enough to describe short-tailed as well as long-tailed data.Some recurence relations for its probabilities and the factorial moments are presente.These recurrence relations are utilized to obtain the minimum chi-square estimators for the parmaters.Maximum likelihood estimators and some other estimators based on first few moments and probabilities are also suggested.Asymptotic relative efficiency of some of these estimators is also obtained and compared.Two test statistics based on the minimum chi-square estimators fo testing some hypotheses regarding the GLSD are proposed.The fit of the model and the application of the test statistics are exemplified by some data sets.Finally, a graphical method is suggested for differentiating between the ordinary logarithmic series distribution and the GLSD.     

Estimation of the parameters in a truncated normal distribution

This paper deals with the estimation of the parameters of doubly truncated and singly truncated normal distributions when truncation points are known. We derive, for these families, a necessary and sufficient condition for the maximum likelihood estimator(MLE) to be finite. Furthermore, the probability of the MLE being infinite is positive. A simulation study for single truncation is carried out to compare the modified maximum likelihood estimator, and the mixed estimator.     

A new test for bivariate distributions : exponential vs new-better-than-used alternative

This paper presents a new test for testing bivariate exponentiality against the bivariate new better than used (BNBU) class of non-exponential probability distributions. The test statistic is a function of U-statistics and hence asymptotically normally distributed and consistent.