Final answer:
The questions pertain to probabilistic and quantitative aspects of statistics, aiming to calculate probabilities and expected values, and to identify the type of data collected (quantitative discrete).
Step-by-step explanation:
The questions presented are focused on the subject of probabilistic and quantitative analysis, specifically within the context of statistics. In question 21, finding the probability that at least four of the 25 patients actually have the flu involves calculating a cumulative probability using a relevant statistical distribution. Question 22 asks for an expected value calculation, which is a fundamental concept in quantitative methodologies, indicating how many patients are expected to have the flu out of every 25 calling in.
Regarding question 23, the data collected about the number of letters in words from a novel is an example of quantitative discrete data. This type of data is numerical and takes on certain values as a result of counting measurements. The context provided points out that quantitative data can be extremely useful for making predictions and understanding patterns, which is essential for fields ranging from meteorology to quantitative sociology and statistical methods in social sciences.