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Characteristics and Examples of Different Levels of Measure


Level Characteristics Example
Nominal Outcomes are qualitative, vary in kind, and fit into one category or another. Categories are mutually exclusive.
* Least precise level of measure
Gender (male=0, female=1);
race/ethnicity (white Hispanic=0, non-white Hispanic=1)
Ordinal Outcomes fit into rank ordered categories; however, the distance between intervals is not known Training level (Intern=1, resident=2, fellow=3, attending=4); Attitudes or preferences (Likert scale - 1=frequently, 3=sometimes, 5=never)
Interval Tells "how much" of something is observed where differences in outcome values have meaning on a scale where the distance between values is known, but there is no meaningful or absolute zero. IQ scores (0 does not reflect an absolute absence of intelligence); H&P checklist items.
Ratio Also measures how much on a meaningful continuum, but zero as an outcome measure has meaning.
* Most precise level of measure

Additional notes about levels of measure: Interval and ratio level variables are often referred to as measurement or quantitative variables, while nominal level variables are referred to as categorical or qualitative. Ordinal level variables are sometimes considered to be in between measurement and categorical.