prosentil

Prosentil, or percentile in English, is a statistic that describes the distribution of a dataset. The p-th percentile is the value below which p percent of observations fall. For example, the 90th percentile is the value below which 90% of the data lie. Percentiles are commonly used to summarize how a value compares with a broader group.

Calculating percentiles from data involves ordering the data from smallest to largest. There are several conventions. The nearest-rank method is simple: the p-th percentile is the value at rank ceil(p/100 × n) in the ordered list of n observations. Other methods compute percentiles by linear interpolation between adjacent data points to give a smoother estimate, especially when p does not correspond to an actual data point. Different conventions can yield slightly different results for the same dataset.

Percentiles are related to quantiles; a percentile is a specific case of a quantile, namely the p/100 quantile. The 50th percentile is the median, and the 25th and 75th percentiles define the first and third quartiles.

Applications of percentiles are widespread. They are used to describe and compare distributions, interpret test scores, and place individual measurements within a reference population. In health and growth monitoring, percentiles help assess whether a measurement such as height or body mass index is typical for age. In finance and weather, percentiles summarize risk or unusualness relative to historical data.

Limitations include dependence on the chosen method and the effects of sample size. Percentiles describe distributional position but do not capture all distributional features alone.