What is a percentile and how might it be used in data analysis?

• A. The maximum value of the dataset.
• B. The minimum value of the dataset.
• C. A value below which a percentage of data falls; used to describe distributions.
• D. The mean value of the dataset.

Answer: (C)

Percentiles tell you the value below which a given proportion of observations fall. They describe where a point sits in the ordered data and help summarize the distribution without assuming any specific shape. For example, the 50th percentile is the median, the 25th percentile marks the point below which 25% of data lie, and the 90th percentile is high up in the distribution. This makes percentiles useful for comparing individuals to a group, setting thresholds, or describing spread—such as saying most scores are below the 80th percentile. They’re more informative about the distribution’s position than just looking at the extremes (maximum or minimum) or the average value (mean). To compute, order the data from smallest to largest and find the value below which p percent fall; with larger data sets you often interpolate between adjacent values.