Measurement in research refers to the process of assigning numbers or categories to characteristics or attributes of individuals or groups in order to quantify and compare them.
The difference between nominal, ordinal, interval, and ratio scales lies in the type of information that they provide.
- Nominal scale: assigns categories or labels (e.g. gender, race) and does not have an inherent order. Example: Assigning labels like "red" or "blue" to a group of objects
- Ordinal scale: assigns categories or labels and has an inherent order (e.g. education level, satisfaction level) Example: Assigning ranks to a group of athletes based on their finish in a race
- Interval scale: assigns equal units of measurement and has an inherent order, but has no true zero point (e.g. temperature measured in Celsius)
- Ratio scale: assigns equal units of measurement, has an inherent order, and has a true zero point (e.g. weight, height, income). Example: measuring the weight of an object in kilograms
The type of scale used can affect the types of statistical analyses that can be performed on the data.