A quality of interest could be the bestselling color for t-shirts sold per week, and the values overtime could be dark blue, dark blue, yellow, and blue for each of the last four weeks.

A quality could also be the fraud risk for a specific month, e.g., low or medium, and the values for the last four months could be low, low, low, and medium.

While the bestselling color for t-shirts is unordered, the fraud risk is. Its three possible values could be low, medium, and high. Hence, qualitative variables with no intrinsic ordering are called nominal, whereas ordered qualitative variables are called ordinal [1].

Reference

  1. A.N. Glaser. High-yield Biostatistics. High-yield series. Lippincott Williams & Wilkins, 2001.
  2. By Denelson83 [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons