Selection between Weibull and lognormal distributions: A comparative simulation study

How to select the correct distribution for a given set of data is an important issue, especially when the tail probabilities are of interest as in lifetime data analysis. The Weibull and lognormal distributions are assumed most often in analyzing lifetime data, and in many cases, they are competing with each other. In addition, lifetime data are usually censored due to the constraint on the amount of testing time. A literature review reveals that little attention has been paid to the selection problems for the case of censored samples. In this article, relative performances of the two selection procedures, namely, the maximized likelihood and scale invariant procedures are compared for selecting between the Weibull and lognormal distributions for the cases of not only complete but also censored samples. Monte Carlo simulation experiments are conducted for various combinations of the censoring rate and sample size, and the performance of each procedure is evaluated in terms of the probability of correct selection (PCS) and average error rate. Then, previously unknown behaviors and relative performances of the two procedures are summarized. Computational results suggest that the maximized likelihood procedure can be generally recommended for censored as well as complete sample cases.

Reliability acceptance sampling plans for the Weibull distribution under accelerated Type-I censoring

Type-I censored reliability acceptance sampling plans (RASPs) are developed for the Weibull lifetime distribution with unknown shape and scale parameters such that the producer and consumer risks are satisfied. It is assumed that the life test is conducted at an accelerated condition for which the acceleration factor (AF) is known, and each item is continuously monitored for failure. Sensitivity analyses are also conducted to assess the effect of the uncertainty in the assumed AF on the actual producer and consumer risks, and a method is developed for constructing RASPs that can accommodate the uncertainty in AF.reliability acceptance sampling plan, Type-I censoring, producer risk, consumer risk, acceleration factor,

Thymic Low Affinity/Avidity Interaction Selects Natural Th1 Cells

Identification of intrathymic eomesodermin+ (Eomes+) CD4 T cells creates a novel idea that there is more than one way for the generation of innate CD4 T cells. Promyelocytic leukemia zinc finger protein+ T cells and natural Th17 cells are known to be generated by sensing a high and persistent TCR strength, whereas this is not the case for Eomes+ CD4 T cells. These cells go through low-level signal during the entire maturation pathway, which subsequently leads to induction of high susceptibility to cytokine IL-4. This event seems to be a major determinant for the generation of this type of cell. These T cells are functionally equivalent to Th1 cells that are present in the periphery, and this event takes place both in transgenic and in wild-type mice. There is additional evidence that this type of Eomes+ innate CD4 T cell is also present in human cord blood.OAIID:oai:osos.snu.ac.kr:snu2015-01/102/0000000922/1ADJUST_YN:NEMP_ID:D026822DEPT_CD:801CITE_RATE:4.922DEPT_NM:의학과SCOPUS_YN:YCONFIRM:

Life test sampling plans for Weibull distributed lifetimes under accelerated hybrid censoring

Life test sampling plan, Hybrid censoring, Producer risk, Consumer risk, Acceleration factor, 62N05,