Quote:
The term percentile and the related term percentile rank are often used in the reporting of scores from norm-referenced tests. For example, if a score is at the 86th percentile, where 86 is the percentile rank, it is equal to the value below which 86% of the observations may be found (carefully contrast with in the 86th percentile, which means the score is at or below the value of which 86% of the observations may be found - every score is in the 100th percentile). The 25th percentile is also known as the first quartile (Q1), the 50th percentile as the median or second quartile (Q2), and the 75th percentile as the third quartile (Q3). In general, percentiles and quartiles are specific types of quantiles.
You know... when they told you in school you were in the 90% Percentile... that means 90% of people were in the group you were in... If your score was '90% percentile'... 90% of people got to that ranking. That is basically the very bottom swimmers on the barrel... This is why EVERYONE is in the 100% percentile - even the guy who dropped out of school on day one.