#statistics 

The **level of measurement** specifies the extent to which a number (or some other [[Data|data]]) actually represents some attribute and, therefore, has implications for the appropriatness of various arithmetic operations and statistical procedures.

## Types
Paired with [[Data in statistics|data types]], these are
- Nominal (qualititative)
- Ordinal (ranked)
- Interval/ratio (quantitative)

### Nominal measurement
The single property of **nominal measurement** is ***classification*** - sorting observations into different classes or categories.

E.g. among students, 1 - male, 2 - female, 3 - other.

arithmetic operations with nominal measurements are meaningless

### Ordinal measurement
Properties: 
- sorts data into classes
- order (1st place, 2nd place, etc)

arithmetic operations are inappropriate (don't know the distance between adjacent ranks)

### Interval/Ratio measurement
Properties:
- sorts data into classes
- order
- equal intervals
- true zero

arithmetic operations are OK

In some cases it's hard to establish an equal interval or a true zero, so they're often used *roughly*.