In this paper, we introduce a new four-parameter generalized version of the Gompertz model which is called Beta-Gompertz (BG) distribution. It includes some well-known lifetime distributions such as beta-exponential and generalized Gompertz distributions as special sub-models. This new distribution is quite flexible and can be used effectively in modeling survival data and reliability problems....

We propose a new family of continuous distributions called the odd generalized exponential family, whose hazard rate could be increasing, decreasing, J, reversed-J, bathtub and upside-down bathtub. It includes as a special case the widely known exponentiated-Weibull distribution. We present and discuss three special models in the family. Its density function can be expressed as a mixture of exp...

this descriptive study is carried out to determine the effectiveness of family planning programmes in iran for years 1991-96. the study revealed the following outlines: contraceptives prevalence rates increased from 42% to 67% during years 1991-96. zaro couples years of protection increased for norplant, injectable contraceptive, iud, vasectomy and tubectomy, but for candom it is decreased in y...

During a 14-month period, 7 patients with hematological malignancies acquired serious infections caused by a single strain of multiply resistant Pseudomonas aeruginosa. A case-control study, culture surveys, and pulsed-field gel electrophoresis implicated a whirlpool bathtub on the unit as the reservoir. All case patients and 32% of control patients used this bathtub (P=.003). The epidemic stra...

In this article, we have developed the discrete version of continuous inverted Nadarajah-Haghighi distribution and called it a distribution. The present model is well enough to not only over-dispersed positively skewed data but can also upside-down bathtub-shaped, decreasing failure rate, randomly right-censored data. Here, some important statistical properties for proposed such as quantile, me...

A new three-parameter extension of the generalized Nadarajah-Haghighi model is introduced and studied. Some its statistical properties are derived. Characterization results presented. The failure rate can be "increasing", "decreasing", "bathtub", "upside-down", "upside-down-constant", "increasing-constant" or "constant". Different non-Bayesian estimation methods under uncensored scheme consider...

Inspired by the successful application of q-Weibull distribution in other research fields, we took lead to use it field medical devices this work. The parameter estimation was performed using probability plot method. CT failure data from Nanfang Hospital Guangzhou, China, were used study reliability equipment at two levels: system and its seven main components. In terms evaluation accuracy, mea...

Many distributions have been used as lifetime models. In this article, we propose a new threeparameter Weibull–Pareto distribution, which can produce the most important hazard rate shapes, namely, constant, increasing, decreasing, bathtub, and upsidedown bathtub. Various structural properties of the new distribution are derived including explicit expressions for the moments and incomplete momen...

The modeling and analysis of lifetimes is an important aspect of statistical work in a wide variety of scientific and technological fields. For the first time the Kum-GEP distribution is introduced and studied. This distribution can have a decreasing and upside-down bathtub failure rate function depending on the value of its parameters; it's including some special sub-model like exponentiated P...

A hazard rate λ(t) is assumed to be of the shape of the “first” part of a “bathtub” model, i.e., λ(t) is non-increasing for t < τ and is constant for t ≥ τ . The isotonic maximum likelihood estimator of the hazard rate is obtained and its asymptotic distribution is investigated. This leads to the maximum likelihood estimator and a confidence interval for a new version of the change point parame...