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Current Trends on Biostatistics
& Biometrics
Research Article
The Gompertz Length Biased Exponential Distribution
and its application to Uncensored Data
Obubu Maxwell
1
*, Oluwafemi Samuel Oyamakin
2
and Eghwerido Joseph Thomas
3
1
Department of Statistics, Nnamdi Azikiwe University, Awka, Nigeria
2
Department of Statistics, University of Ibadan, Ibadan, Nigeria
3
Department of Mathematics and Computer Science, Federal University of Petroleum Resources, Effurun, Nigeria
*Corresponding author: Obubu Maxwell, Department of Statistics, Nnamdi Azikiwe University, Awka, Nigeria
Received: February 22, 2019 Published: March 08, 2019
Introduction
Length biased distributions are special case of the more
general form known as weighted distribution [1], first introduced
by [2] to model ascertainment bias and formalized in a unifying
theory by [3]. Lifetime data may be modeled with several existing
distributions, although the existing models are not adequate or are
less representative of actual data in many situations. Therefore, the
development of compound distributions that could better describe
certain phenomena and make them more flexible than the baseline
distribution is of great importance [4]. Thus, the choice of the model
is also an important issue for reliable model parameter estimation.
Some exponential distribution generalizations for modeling
lifetime data due to some interesting advantages have been recently
proposed [5]. In recent years many exponential distribution
generalizations have been developed, such as the Marshall
Olkin length biased exponential distribution [5], exponentiated
exponential [6,7], generalized exponentiated moment exponential
[8], extended exponentiated exponential [19], Marshall-Olkin
exponential Weibull [10], Marshall-Olkin generalized exponential
[5], and exponentiated moment exponential [11] distributions.
A random variable X is said to have a length biased exponential
distribution with parameter \beta if its probability density function
(pdf) and cumulative distribution function (cdf) is given by
equation (1) and (2) respectively [12]:
2
(, ) , 0, 0
x
x
gx e x
β
β β
β
−
= > > (1)
() 1 (1 ) , 0, 0
x
x
Gx e x
β
β
β
−
= − + > > (2)
Where is the scale parameter.
The survival function is given by the equation
() (1 ) , 0, 0
x
x
Sx e x
β
β
β
−
= + > >
(3)
The hazard function is
() , 0, 0
(1 )
x
x
x
e
Hx x
x
e
β
β
β
β
β
−
−
= > >
+
(4)
Abstract
This paper proposes a generalization of the length biased exponential distribution, called the Gompertz length biased
exponential (GLBE) distribution. Some of the basic properties of the proposed model were derived in minute details and model
parameters estimated by the maximum likelihood estimate method. The adequacy of the model is empirically validated with the
use of real - life data.
Keywords: Exponential Distribution; Length Biased; Gompertz Generalized Family Of Distribution; Quantile Function; Hazard
Functions; Survival Function
ISSN: 2644-1381
DOI: 10.32474/CTBB.2019.01.000111