Perspective on variables in medical research.

Research concepts cannot be materialized until and unless study variables are carefully selected and clearly defined. However, emphasis on variables is not limited to data collection. It should be envisioned from the start that the contents of the variables recorded are congruent with the statistical analysis suggested. These two processes require a comprehensive understanding of variables in epidemiology and biostatistics disciplines. In this article classifications are discussed keeping in view their utility in medical research.