Raw data and statistical analysis in the SPSS program of a retrospective cohort epidemiological study (2015 to 2020) that investigated the effect of tail docking on the occurrence of myiasis in a herd of sheep in Brazil.
This is an epidemiological study of the retrospective cohort type in an experimental herd of sheep with a time frame of six years (2015 to 2020), where the outcome of interest was the monthly incidence of myiasis, and the main predisposing factor studied was the effect of the presence or absence of the tail on animals. The time unit adopted was the month and the experimental unit was each sheep in the herd. The incidence was calculated considering the occurrence of cases of myiasis as a dichotomous variable, thus generating two possibilities for categorization: animal with myiasis or animal without myiasis in each month. The classic actuarial method was used to calculate the incidence rates, weighted by the number of individuals at risk in the corresponding month. This choice aimed to control the effect of entry and exit of animals from the herd during the study period. Thus, the values for incidence are presented in percentage rates that are the result of the absolute division of the “number of sheep affected by myiasis in the month” by the “number of sheep in the herd in the same month”. The incidence rate of myiasis was the outcome of interest in the study. Relative risk (RR) and odds ratio (OR) were the association measures used in this study. The incidence rate ratio (IRR) was used as an aid to evaluate the effectiveness of tail docking to reduce the incidence of myiasis.
Steps to reproduce
Run the SPSS-code (spv document) to reproduce the analyses using the raw data (csv document).