[Basic Statistical Measures for Dichotomous Data Formats: Risk, Odds, Logits, Relative Risk, Odds Ratio]

In rehabilitation science dichotomous data formats are frequently used to indicate or analyze patient characteristics. Although underlying information may be more fine graded, dichotomous or dichotomized data formats like 'yes vs. no', 'salient vs. not salient' or 'capable to work vs. not capable to work' are often adequate information formats for communication or decision making purposes. Definitions and properties of risk, odds and logits - typically applied in rehabilitation research - are outlined as frequency measures of occurrence. The association of two variables can be characterized by relative risk, risk reduction, logit reduction, odds ratio and ln(odds ratio). As odds ratio is independent from base rates it reflects association strength unambiguously. Hence, important correlational measures are defined as functions of odds ratio. It will be illustrated that statistical aspects as well as aspects regarding comprehensibility of the represented information are decisive to select appropriate measures and present data information appropriately.