Eucalyptus cloeziana seed count data: a comparative analysis of statistical models

Thomas Bruno Michelon,Maristela Panobianco,Cesar Augusto Taconeli,Elisa Serra Negra Vieira

doi:10.1590/1413-7054201943020619

Thomas Bruno Michelon, Maristela Panobianco + Show 2 more

Open Access

https://doi.org/10.1590/1413-7054201943020619

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Abstract

ABSTRACT Generalized linear models (GLMs) are an extension of the linear model and include the normal, Poisson, and negative binomial distributions. Although GLMs were introduced in 1972, most seed technology studies, especially those involving count data, such as germination tests of seeds from the genus Eucalyptus, still using the analysis of variance, without analysis of the fit of other models. Thus, this study aimed to evaluate the most appropriate model in the GLM class for seed count data of Eucalyptus cloeziana. Data were obtained from a germination test using seeds from three lots of E. cloeziana. Each lot was separated by sieving into three material fractions based on size: small (<0.84 mm), medium (from 1.18 to 1.00 mm), and large (>1.18 mm). The data analysis was based on the use of GLMs adjusted to normal, Poisson, and negative binomial distributions, and the models were evaluated by the Akaike and Bayesian Schwartz criteria and Cook’s distance and half-normal diagnostic graphs. Compared to other adjustments, the normal distribution adjustment differed in the configuration of means submitted to the Tukey test, and although the data met all normality assumptions, the adjustment with the Poisson distribution was the most suitable for the count data from a germination test of E. cloeziana seeds.

Highlights

Count data can be conceptualized as representing how often a specific event occurs, resulting in nonnegative integer values (Kosma et al, 2019)
The viability of a lot can be determined by a germination test, which according to the evaluated species, can be conducted by repeatedly measuring a fixed number of seeds or using a specific seed weight, the latter of which is recommended for Eucalyptus seeds, the most cultivated forest genus in Brazil, which accounts for approximately 73% of the total planted forest area (Ibá, 2019)
Among Eucalyptus species, Eucalyptus cloeziana stands out for its strong and durable wood, which presents a greater density than the wood of other species within the genus and is commonly used in construction and highadded value products, such as furniture (Hicks; Clark, 2001; Boland et al, 2006; Li et al, 2017)

Summary

Introduction

Count data can be conceptualized as representing how often a specific event occurs, resulting in nonnegative integer values (Kosma et al, 2019). The viability of a lot can be determined by a germination test, which according to the evaluated species, can be conducted by repeatedly measuring a fixed number of seeds (expressed as a percentage of normal seedlings) or using a specific seed weight (number of normal seedlings), the latter of which is recommended for Eucalyptus seeds, the most cultivated forest genus in Brazil, which accounts for approximately 73% of the total planted forest area (Ibá, 2019). Among Eucalyptus species, Eucalyptus cloeziana stands out for its strong and durable wood, which presents a greater density than the wood of other species within the genus and is commonly used in construction and highadded value products, such as furniture (Hicks; Clark, 2001; Boland et al, 2006; Li et al, 2017). There is an orthodoxy in the choice of the model, in which the ANOVA model is preferable because it is more traditional rather than because it presents a better fit (Sileshi, 2012; Santana; Carvalho; Toorop, 2018)

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