Next Lapin makes a distinction between interval and ratio data. This typology of measurement scales was defined in the 1940's by Harvard psychologist S. S. Stevens. For statistical purposes and for this course, I don't find the distinction between interval and ratio data interesting or useful. So don't worry about telling the difference between the two. A more important distinction in this course is between discrete and continuous data.
Discrete data are data for which there are a finite or countably finite number of possible values.
We emphasize the difference between discrete and continuous data in the second half of the course. In particular, continuous data requires calculus for proper anlysis. This page was last modified on August 21, 2001.