Final answer:
The descriptive stat that must have the numbers in order is the median. It represents the middle value of a numerically ordered data set.
Step-by-step explanation:
The descriptive stat that must have the numbers in order to be calculated is the median. Unlike the mode or the mean, the median requires the data to be sorted because it is the middle number in a set of numbers when arranged in numerical order. If there is an even number of observations, the median is the average of the two middle numbers.
For example, consider the data set: 4, 5, 6, 6, 7, 7, 8, 9. With this ordered set, the median would be 6.5, as it is the average of the two middle numbers 6 and 7. Descriptive statistics such as the mean, the median, and the mode are crucial for summarizing different aspects of the data. The mean, calculated as the total of all values divided by the number of values, is sensitive to extreme outliers. The mode, being the most frequently occurring value in a set, doesn't require ordering.