IEOR Seminar by Anup Dewanji

Title: Analysis of sequential quality improvement plans to obtain confidence bounds
 
Speaker: Prof. Anup Dewanji, Indian Statistical Institute, Kolkata
 
Day, Date and Time: Thursday, 8th December 2022, 10 AM. 
 
Venue: Seminar Hall, Second Floor, IEOR Building.
 
Abstract: Sequential quality improvement plans create a series of product versions with improving reliability by addressing the failure modes of the previous versions. They represent a widely used reliability improvement strategy. Reliability metrics for the current product version need to be estimated from the failure times of the previous versions. Confidence bounds of the reliability metrics are of more importance to decision-makers than point estimates as they allow for an evaluation of a margin of reliability in the product. The availability of exactly one failure time for each product version poses a challenge for obtaining this confidence bound. In this article, we consider a model in which the time to failure distributions belong to a family of distributions indexed by a real valued parameter, whose ordering determines the stochastic ordering of the distributions. We do not make any assumptions about the nature of improvement in reliability, allow for no improvement in reliability for some consecutive versions and relax the requirement of independence of the failure times. We propose a novel statistic, based upon the maximum of the observed failure times, which is proved to be a confidence bound for the parameter of interest with a minimum specified coverage probability. Since the proposed method makes very few assumptions about the nature of the reliability improvement and does not use asymptotic theory, it may be ideal for the analysis of time to failure data for catastrophic failures where one would expect few failures. If required, we propose a method for ensuring the monotonicity of the confidence bounds. The methods developed are applied to datasets relating to software debugging and a new dataset derived from an automated error logger. The analysis reveals some surprising insights. 
 
Speaker's Bio: Prof Dewanji is currently a Professor at the Indian Statistical Institute, Kolkata. He completed his undergraduate and Masters in Statistics from Indian Statistical Institute, Kolkata, India, and received his PhD in Statistics from the University of Waterloo in Canada. Prof Dewanji did his research work as a Post-Doctoral Fellow in Health and Welfare in Canada for two and half years and then he worked as a Staff Scientist in Fred Hutchinson Cancer Research Center, Seattle, USA, before returning to India to join the Indian Statistical Institute in 1988.
His research is focused on Survival Analysis, Reliability, Cancer Modeling, Epidemiology, Clinical Trials and Applied Stochastic Processes. He has written nearly 100 papers in peer-reviewed journals.