Which of the following best exemplifies descriptive statistics?

• A. 95% confidence interval for the mean age this month.
• B. Mean age of patients in the clinic this month.
• C. P-value for a test comparing ages.
• D. Hypothesis test results for age differences.

Answer: (B)

Descriptive statistics involve summarizing and describing the features of a data set. The mean age of patients in the clinic this month is a direct, single-number summary of the ages actually observed, describing the sample itself without making claims about a larger group or about uncertainty. It’s the classic example of describing data as they appear.

In contrast, a 95% confidence interval for the mean age goes beyond the observed data to estimate a population parameter and quantify uncertainty. A P-value for a test and results from a hypothesis test are all about making inferences or generalizing beyond the sample, assessing whether observed differences could occur by chance under a null hypothesis.

So the mean age of patients in the clinic this month is the best example of descriptive statistics because it summarizes the data you have without inferring beyond it.