Variables: their graphical representations and descriptive statistics

Variables: their graphical representations and descriptive statistics Whatever the research question, it is necessary to collect and analyze a data set commonly named in statistics "set of variables". There are two main groups of variables: the quantitative variables and the qualitative variables, which can be subdivided into several subgroups. The statistical methods used differ according to the type of variables. The first step of data analysis is to indentify the different types of variables since the choice of statistical methods will depend. This statistical note describe the different types of variables that may be encountered in medical research. The main graphical representations (histogram, box plot, bar chart, pie chart) and descriptive statistics (frequency, percentage, mean, standard deviation, median, interquartile range) used to summarized the data are also presented.