Percentile

A Percentile is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations falls. For example, the 20th percentile is the value (or score) below which 20 percent of the observations may be found. The term percentile and the related term percentile rank are often used in the reporting of scores from norm-referenced tests.

Definition

The nth percentile of a set of data is the value at which n percent of the data is below it. In everyday life, percentiles are used to understand values such as test scores, health indicators, and other measurements.

Calculation

There are several different methods for calculating percentiles. The most common method is the "standard" method, where the nth percentile is found by sorting the data and finding the value that corresponds to the nth percent of the data. Other methods include the "weighted" method, where the data is weighted according to some factor, and the "interpolation" method, where the nth percentile is estimated by interpolating between the values of the data.

Uses

Percentiles are often used in education to compare student scores. For example, if a student scores in the 90th percentile on a standardized test, it means that they scored better than 90% of the students who took the test.

In medicine, percentiles are used to track a patient's growth and development. For example, a child's height and weight percentiles are often tracked over time to ensure they are growing at a healthy rate.

In business, percentiles can be used to understand and analyze data. For example, a business might use percentiles to understand customer satisfaction scores or sales data.

See also

• Quartile
• Decile
• Percentile rank
• Standard score

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  Standard deviation diagram
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  Percentile
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  Percentile interpolation