Final answer:
Descriptive statistics like mean, median, and mode are essential for summarizing data, while correlation is relevant when considering the relationship between two variables, and conditional percentages help with understanding data categories.
Step-by-step explanation:
When analyzing data, an appropriate numerical summary to include would be descriptive statistics, such as mean, median, and mode, which help identify the center of the data. Another important set of statistics are measures of variability like standard deviation and variance which provide information about the spread of the data. If the focus is on the relationship between two variables, the correlation (r) would be considered. When discussing the proportion of occurrences within different categories, considering conditional percentages can be insightful. These summaries are fundamental in the field of descriptive statistics.