Variability is a complex concept with many facets.<br>Students build up their understanding of variability over time.<br>Variability is used for descriptive purposes, but is also an essential concept for understanding inference (sampling distributions, confidence intervals, p-values, etc.)<br>Therefore, helping students develop an understanding of variability (how it is measured, what it represents, how it is represented, how to use it to make comparisons) may require revisiting the concept throughout the course.