The different types of scale variables are nominal, ordinal, interval, and ratio. Variables are measurements made using an instrument, device, or computer. The scale of the variable measured drastically affects the type of analytical techniques that can be used on the data, and what conclusions can be drawn from the data. There are four scales of measurement: nominal, ordinal, interval, and ratio. Understanding these scales is fundamental in data analysis and statistics.
Here's a breakdown of each scale:
The Four Scales of Measurement
Nominal Scale
- Definition: The nominal scale is the most basic level of measurement. Variables on this scale are used purely for labeling or categorizing data.
- Properties: Data can be categorized, but there is no intrinsic order or numerical value associated with the categories. You can count frequencies within categories but cannot perform mathematical operations like addition or subtraction between them.
- Examples:
- Gender (Male, Female, Non-binary)
- Marital Status (Single, Married, Divorced)
- Eye Color (Blue, Brown, Green)
- Types of fruit (Apple, Banana, Orange)
Ordinal Scale
- Definition: The ordinal scale allows for data to be categorized and ordered or ranked.
- Properties: Data has a rank order, but the intervals between the ranks are not necessarily equal or meaningful. You know that one category is "more" or "less" than another, but not by how much.
- Examples:
- Satisfaction levels (Very Dissatisfied, Dissatisfied, Neutral, Satisfied, Very Satisfied)
- Educational attainment (High School, Bachelor's, Master's, PhD)
- Ranking in a competition (1st place, 2nd place, 3rd place)
- Likert scales (e.g., Strongly Disagree to Strongly Agree)
Interval Scale
- Definition: The interval scale builds upon the ordinal scale by having ordered categories where the intervals between values are equal and meaningful.
- Properties: Data has order, equal intervals between values, but lacks a true zero point. This means zero doesn't represent the absence of the measured attribute. You can perform addition and subtraction, but not multiplication or division in a way that implies ratios.
- Examples:
- Temperature in Celsius or Fahrenheit (0°C or 0°F doesn't mean no temperature)
- Calendar years (The year 0 doesn't mean time didn't exist)
- IQ scores (An IQ of 0 doesn't mean zero intelligence)
Ratio Scale
- Definition: The ratio scale is the highest level of measurement. It possesses all the properties of the interval scale, plus a true zero point.
- Properties: Data has order, equal intervals, and a true zero point. A true zero means that zero represents the complete absence of the measured attribute. This allows for all mathematical operations, including multiplication and division, and meaningful ratios can be calculated.
- Examples:
- Height (0 cm means no height)
- Weight (0 kg means no weight)
- Age (0 years means not born yet)
- Income (0 dollars means no income)
- Number of items sold (0 items means none were sold)
Summary of Scale Properties
| Scale Type | Categories | Order | Equal Intervals | True Zero |
|---|---|---|---|---|
| Nominal | Yes | No | No | No |
| Ordinal | Yes | Yes | No | No |
| Interval | Yes | Yes | Yes | No |
| Ratio | Yes | Yes | Yes | Yes |
Understanding these scales is crucial for choosing appropriate statistical methods and accurately interpreting data.
