This document defines and provides examples of different types of variables and levels of measurement. There are two main types of variables: qualitative/attribute variables where the characteristic is non-numeric like gender or eye color; and quantitative variables where information is reported numerically like account balances or number of children. Quantitative variables can be discrete, taking on certain numeric values with gaps, or continuous, assuming any value within a range. There are also four levels of measurement: nominal for unordered categories; ordinal for ordered but not precisely differentiated categories; interval for ordered and precisely differentiated categories without a true zero; and ratio which has all interval properties plus a true zero point.