Percentiles

Where quartiles cut a distribution into four parts, percentiles cut it into one hundred equal parts, giving 99 dividing positions denoted $P_1, P_2, P_3, \ldots, P_{99}$. The $50^{\text{th}}$ percentile, $P_{50}$, coincides with the median.

A percentile tells you your relative standing. Scoring in the 82nd percentile in an entrance examination means you are placed above 82 per cent of the candidates — equivalently, only 18 per cent scored higher than you. So if one lakh (1,00,000) students appeared, roughly 18,000 would …