Concepts: an abstract definition for characteristics of or types of phenomena, groups or individuals. Variable: a measurable property of a phenomenon, group, person that can potentially take on different values, derived to capture a concept, variation across cases or over time. Measure: a procedure for determining whether or to what degree a concept applies to specific cases based on observation of those cases. Intrinsic parts/components of a concept that are independent of one another and are neither causes nor consequences of the concept. Interval: numerical in nature, difference in values indicates how much more or less of something. Independent variable: a variable that captures the purported cause of the causal claim (x) Dependent variable: a variable that captures the purported outcome of the causal claim (y) Measurement error: refers to weak validity or weak reliability, the two types of measurement error are measurement bias (systematic measurement error) and random measurement error. Upward bias: when cases have extraneous features.