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Under-dispersed count data often appear in clinical trials, medical studies, demography, actuarial science, ecology, biology, industry and engineering. Although the generalized Poisson (GP) distribution possesses the twin properties of under- and over-dispersion, in the past 50 years, many authors only treat the GP distribution as an alternative to the negative binomial distribution for modeling over-dispersed count data. To our best knowledge, the issues of calculating maximum likelihood estimates (MLEs) of parameters in GP model without covariates and with covariates for the case of under-dispersion were not solved up to now. In this paper, we first develop a new minimization–maximization (MM) algorithm to calculate the MLEs of parameters in the GP distribution with under-dispersion, and then we develop another new MM algorithm to compute the MLEs of the vector of regression coefficients for the GP mean regression model for the case of under-dispersion. Three hypothesis tests (i.e., the likelihood ratio, Wald and score tests) are provided. Some simulations are conducted. The Bangladesh demographic and health surveys dataset is analyzed to illustrate the proposed methods and comparisons with the existing Conway–Maxwell–Poisson regression model are also presented. [ABSTRACT FROM AUTHOR]

The study was conducted to assess key factors influencing suspected white spot syndrome virus ( WSSV) disease and associated shrimp production and economic performance in three contrasting black tiger shrimp ( P enaeus monodon) culture technologies promoted by the United States Agency for International Development funded Shrimp Quality Support Project ( SQSP) in Bangladesh. A total of 350 traditional, 315 Modified Traditional Technology1 ( MTT1), 36 MTT2 and 88 Closed System Technology ( CST) farmers from 10 sub-districts in three districts of Khulna division were surveyed following random sampling at the end of the project. Binomial probit regression analysis revealed that smaller newly constructed ponds (known locally as gher) were less susceptible to WSSV, provided aquatic weeds were controlled using chemicals. Removal of sludge from ghers also had a positive effect, irrespective of technology and location. It was also shown that stocking of screened shrimp postlarvae ( PL) does not guarantee protection against WSSV ( t = 1.39, P > 0.05). Higher shrimp production was obtained by farmers practicing CST, followed by those operating MTTs and traditional technology respectively. Farmers who adopted CST also gained higher profitability followed by those operating MTT1, MTT2 and traditional technology. [ABSTRACT FROM AUTHOR]