Title: Thinking ahead to analysis: Levels of measurement
Course: UGQuants (SSPS) > Section: Survey Design

Thinking ahead to analysis: Levels of measurement

When developing our questionnaire content, it is important to think ahead to the analysis stage of the research. The level of measurement of a variable, i.e. interval/ratio, ordinal or nominal, is key to the types of statistical analysis we can undertake. The response structure to our questions will determine the level of measurement.

For example, if we are interested in whether a respondent has any children, we could ask any of the following questions:

- Are you a parent? Yes or no
- How many children do you have: 1, 2 or 3 plus?
- How many children do you have?: .........

Each of these questions is essentially the same variable but the level of measurement is different. It is generally regarded as better to measure at the highest possible level i.e. interval level as this enables a wider range of statistical techniques to be employed. Furthermore, it is possible to collapse interval variables into lower level response categories but the reverse is not possible.