NOCP Competency for COPR Practice Exam 2026 - Free COPR Practice Questions and Study Guide

Descriptive statistics are about summarizing and describing the data you have. They give a clear picture of what the data look like: the average value, how spread out the values are, where most data fall, and how often different categories occur. They apply to the data at hand; if you have data for the entire group, that’s still descriptive, but it doesn’t go beyond those observed numbers.

Inferential statistics use the information in a sample to make educated guesses about a larger population. They rely on probability theory to quantify uncertainty, allowing you to estimate population parameters (like the true mean) with a confidence interval or to test whether observed differences could plausibly exist in the whole population.

A helpful way to see the difference is to think about a survey: reporting the average rating and the spread for the respondents you collected describes your sample. Concluding that the population’s average rating is likely within a certain range or that a difference between groups is statistically significant involves making inferences about the population.