1.7 Categorical Data Types: Ordered and Unordered

The drink sizes at Starbucks are an example of ordered categorical data.  Tall, Grande, Venti, and Treinta are each categories, but the labels are not just arbitrary distinctions; instead, these exist along a spectrum, starting with the smallest drink size and moving towards the largest.  The same is true with t-shirt sizes at your nearby department store:  Extra Small, Small, Medium, Large, and Extra Large are categories, but they have an inherent ordering.  

More typically, we will encounter unordered categorical data.  Categorical data is unordered whenever its levels have no inherent hierarchy.  That local retailer might offer five different t-shirt colors:  blue, brown, purple, red, and black.  Each of these colors is simply a distinct option.