An independent variable is a variable that is being for making comparisons.
For instance the scientist might wonder if there is a difference between men and women, so the independent variable is gender (with two values: man or woman). A second example: there might be a difference between students who attended a course and students who did not. Again this is one variable (attended a course) with two values (yes or no). A third example: is there a difference between countries. This is one variable (country) with a lot of possible values. A fourth example: differences in age.
A dependent variable can be measured at a nominal, ordinal, interval or ratio scale. This is another way to classify variables, and this is explained elsewhere in this dictionary. You must know both classifications, because both determine the type of analysis that you can perform with these variables. Read all about it in my paper called How to choose the correct statistical test?
Related topics to independent variable
- Experimental variables
- Dependent variable