1. The problem asks to identify the type of statistics used when a professor states the average age of all students based on a sample. 2. The formula or concept here is understanding types of statistics: descriptive statistics summarize data from a sample or population, inferential statistics make predictions or inferences about a population based on a sample. 3. Since the professor uses sample data to infer about the entire university, this is an example of **inferential statistics**. Final answer: B. Inferential statistics