In response to the COVID-19 pandemic, governments worldwide have implemented social distancing policies with different levels of both enforcement and compliance. We conducted an interrupted time series analysis to estimate the impact of lockdowns on reducing the number of cases and deaths due to COVID-19 in Brazil. Official daily data was collected for four city capitals before and after their respective policies interventions based on a 14 days observation window. We estimated a segmented linear regression to evaluate the effectiveness of lockdown measures on COVID-19 incidence and mortality. The initial number of new cases and new deaths had a positive trend prior to policy change. After lockdown, a statistically significant decrease in new confirmed cases was found in all state capitals. We also found evidence that lockdown measures were likely to reverse the trend of new daily deaths due to COVID-19. In São Luís, we observed a reduction of 37.85% while in Fortaleza the decrease was 33.4% on the average difference in daily deaths if the lockdown had not been implemented. Similarly, the intervention diminished mortality in Recife by 21.76% and Belém by 16.77%. Social distancing policies can be useful tools in flattening the epidemic curve.

Introduction: What if my response variable is binary categorical? This paper provides an intuitive introduction to logistic regression, the most appropriate statistical technique to deal with dichotomous dependent variables. Materials and Methods: we estimate the effect of corruption scandals on the chance of reelection of candidates running for the Brazilian Chamber of Deputies using data from Castro and Nunes (2014). Specifically, we show the computational implementation in R and we explain the substantive interpretation of the results. Results: we share replication materials which quickly enables students and professionals to use the procedures presented here for their studying and research activities. Discussion: we hope to facilitate the use of logistic regression and to spread replication as a data analysis teaching tool.

The transformation of quantitative variables into categories is a common practice in both experimental and observational studies. The typical procedure is to create groups by splitting the original variable distribution at some cut point on the scale of measurement (e.g. mean, median, mode). Allegedly, dichotomization improves causal inference by simplifying statistical analyses. In this article, we address some of the adverse consequences of recoding quantitative variables into categories. In particular, we provide evidence that categorization usually leads to inefficient and biased estimates. We believe that considerable progress in our understanding of data analysis can occur if scholars follow the recommendations presented in this article. The recodification of quantitative variables as categorical is a poor methodological strategy, and scientists must stay away from it.

The intentional killing of one human being by its own kind is considered the worst of the crimes. Therefore, homicide prevention is a major concern for policy makers in both developing and developed countries. We propose regression modeling for the homicide rates in Brazil along with appropriately chosen distributions for these responses that are in agreement with the restriction of values to the unit interval. We adopt the beta and simplex regression models with systematic components for the mean and dispersion parameters to explain the homicide rates in 27 state capitals of Brazil from the following explanatory variables: time, Gini coefficient, municipal human development index (MHDI), illiteracy and poverty rates. We employ standard likelihood techniques, perform influence and residual analysis and calculate goodness-of-fit statistics to select the best regression to explain homicides rates in these capitals. We perform the computations in the R package. The main results suggest the following: the mean homicide rate is increasing over time; there is a negative correlation between MHDI and murder rate; the poverty has a quite small negative impact on the mean homicide rates in the beta regression. The Gini coefficient and the illiteracy and poverty rates explain the dispersion of the homicide rates.

Quais os caminhos adotados rumo a democratização pelos países que passaram pela Primavera Árabe e tiveram seus governos depostos? O objetivo do artigo é analisar os índices de democracia eleitoral dos países que tiveram governos depostos pela Primavera Árabe (Tunísia, Egito, Iêmen e Líbia). A hipótese de trabalho sustenta que a quebra de regime destes países levou a um percurso de aumento simultâneo dos direitos civis e políticas. Em outras palavras, a quebra de regime levou a um aumento simultâneo das duas dimensões que levam à Poliarquia: contestação e inclusividade. Para testar essa hipótese, adotou-se uma abordagem quantitativa através de análise descritiva dos índices de democracia, liberdade civil e direitos presentes no Varieties of Democracy (V-Dem), no Freedom House e os indicadores de contestação e inclusividade presentes no Quality of Government (QoG). Os resultados sustentam que apenas Tunísia e Líbia apresentaram uma evolução simultânea de liberdades civis e políticas após 2011 e apenas a Tunísia realizou a transição para um regime democrático.