Variables in empirical analyses sit at the basic level, so variable means concept.

Evidence

“Variable” often means concept in the context of this book. Standard usage in statistical analyses uses expressions like “indicator of a variable.” Since variables in empirical analyses, models, theories, and hypotheses typically lie at the basic level, that means variable = concept for the purposes of this volume. — Gary Goertz, Social Science Concepts and Measurement, 375

Categorization

• DEFINE: Goertz collapses the variable/concept distinction for measurement purposes, treating them as equivalent at the basic level of analysis.