Modelos série de potência com excesso de zeros observáveis e latentes
Fecha
2016-09-28Autor
Coaguila Zavaleta, Katherine Elizabeth
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The present work's main objective is to study the significance of zeros in an observable
and latent data. In observable data set that occur excess of zeros, its common to have
sobredispersion. In this sense, the models zero-inflated power series (ZISP) were proposed
to accommodate these excesses. Specifically for the analysis of observed data, it was made
a study of gradient statistic, proposed by Terrell (2002), to test the hypotheses in relation
to inflation parameter ZISP models. This test is based on evaluation of the performance
of gradient statistic compared with the classical likelihood ratio (Wilks, 1938), score (Rao,
1948) and Wald (Wald, 1943) statistics. In addition, recently, fragility has being modeled
by discrete distributions using non-negative integers values that allows zero fragility, which
means, individuals who do not present the event of interest (fraction of zero risk). For this
type of latent data, we have proposed a new survival model induced by discrete frailty with
ZISP distribution. This proposal brings a real description of individuals without risk, because
individuals cured due to genetic factors (immune) are modeled by fraction of deterministic
zero risk, while the cured by treatment are modeled by fraction of random zero risk. In this
context, we also developed the gradient statistic to verify parameter significance of zero risk
for data modeled by fraction of deterministic zero risk. To show our proposals, we present
the results of simulation studies and applications using real data.