Definition
A percentile is a statistical measure indicating the position of a value within a dataset when arranged in ascending order. The k-th percentile means that k% of the data falls at or below that value. It provides a way to understand relative standing within a distribution.
Calculation Method
For n data points sorted in ascending order, the position of the k-th percentile is calculated as (k/100) x (n+1). When this value is not an integer, linear interpolation between adjacent values is used. Different software packages may use slightly different interpolation methods.
Common Percentiles
The 25th percentile (Q1) is the first quartile, the 50th percentile is the median, and the 75th percentile (Q3) is the third quartile. The difference Q3 - Q1 is called the interquartile range (IQR) and measures the spread of the middle 50% of the data.
Application in MyRank
MyRank calculates where a user's input value falls as a percentile within the global population and displays it as a world ranking. For example, being at the 90th percentile means you are in the top 10% worldwide.