Why transform continuous variables into categorical variables?
From PsychWiki - A Collaborative Psychology Wiki
It is possible to transform continuous variables into categorical variables
- "Dichotomizing" is where you split a continuous variable into a categorical variable that has two levels.
- Imagine a study about happiness where your happiness question (or composite) ranges from 1 to 7. You might be interested in categorizing the subjects as either high happiness (4 through 7 on the scale) or low happiness (1 through 4 on the scale). This is called "dichotomizing" the variable because you are creating a new variable that has only two options.
- You can also split a continuous variable into thirds, fourths, fifths, or as many different categories as you wish.
- Another example of why you would want to transform a continuous variable into a categorical variable is if there are only a few responses on some of the answer choices in the continuous variable. - Imagine a scale range from 1-11 in which answer choice 4 and answer choice 9 received only 1 response each. One response is not enough data for meaningful interpretation. You may want to collapse the 11 point scale into 3 or 4 categories.
- Keep in mind that creating the new categorical variable is answering a different research question than the original continuous variable. When you splice the continuous variable into categories, any data analysis using the new categorical variable must be interpreted in line with the categories.
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