If you know about medians, you should also know about percentile ranks. Percentile ranks are used to define the percentage of cases equal to or below a certain point in a distribution or set of scores. For example, if a score is “at the 75th percentile,” it means that the score is at or above 75% of the other scores in the distribution. The median is also known as the 50th percentile, because it’s the point at or below which 50% of the cases in the distribution fall. Other percentiles are useful as well, such as the 25th percentile, often called Q1, and the 75th percentile, referred to as Q3.
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