This document discusses different levels of measurement in statistics:
- Nominal level deals with categorical variables without ordering. Examples include gender and team jersey numbers.
- Ordinal level also deals with categorical variables but includes ordering. Examples include socioeconomic status and exam difficulty.
- Interval level includes order and distance between units but no absolute zero. Examples include Celsius temperature and IQ scores.
- Ratio level includes all properties of interval plus a true absolute zero point. Examples include mass, height, and electric charge.