Quoting NIST, when analyzing a continuous variable, one needs to validate four assumptions that typically underlie all measurement processes; namely, that the data at hand "behave like":
- random drawings;
- from a fixed distribution;
- with the distribution having fixed location; and
- with the distribution having fixed variation.
The 4-plot is a great way to validate these assumptions.
My questions are the following:
- What are equivalent assumptions for a discrete variable?
- What would be the best set of graphics to validate them?