In statistics, what is a statistic?

• A. A fixed population value.
• B. A numeric summary calculated from a sample.
• C. A summary of the entire population.
• D. A theoretical distribution.

Answer: (B)

A statistic is a numeric summary calculated from a sample. This means you take data from a subset of the population and compute a number like the mean, proportion, standard deviation, or correlation. That number describes the sample and is used as an estimate of the corresponding population parameter—the true value for the entire group, which is fixed but usually unknown. For example, the average height of the people in your sample is a statistic. The true average height of everyone is a parameter. The other options refer to the entire population value or to a theoretical distribution, not to a single numeric summary derived from sample data.