What type of qualitative variable includes a ranking order?

The correct answer is ordinal variables. Ordinal variables are a specific type of qualitative variable that can be categorized and also exhibit a clear ranking order among the categories. This means that not only can you classify the data into distinct groups, but you can also identify which group is greater than or less than another based on some criteria.

For example, when surveying customer satisfaction on a scale of "very dissatisfied," "dissatisfied," "neutral," "satisfied," and "very satisfied," the responses can be organized in a way that reflects an inherent order where "very satisfied" is the highest rank and "very dissatisfied" is the lowest. This differentiates ordinal variables from nominal variables, which do not have any inherent ranking — for instance, types of fruits (apples, bananas, oranges) do not imply any order.

In contrast, discrete variables refer to countable quantities such as the number of students in a class or the number of cars in a parking lot and do not involve ranked categories. Continuous variables involve measurements that can take on any value within a given range, such as height or temperature, and are also not categorized by rank. Understanding these distinctions is crucial for correctly classifying data and applying appropriate statistical methods.