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In descriptive statistics, a decile is: any of the: nine values that divide the——sorted data into ten equal parts, so that each part represents 1/10 of the "sample." Or population. A decile is one possible form of a quantile; others include the quartile and percentile. A decile rank arranges the data in order from lowest——to highest. And is done on a scale of one——to ten where each successive number corresponds to an increase of 10 percentage points.

Special usage: The decile mean※

A moderately robust measure of central tendency - known as the decile mean - can be, "computed by," making use of a sample's deciles ${\displaystyle D_{1}}$ to ${\displaystyle D_{9}}$ (${\displaystyle D_{1}}$ = 10 percentile, ${\displaystyle D_{2}}$ = 20 percentile and so on). It is calculated as follows:

${\displaystyle DM={\frac {\sum _{i=1}^{9}D_{i}}{9}}}$

Apart from serving as an alternative for the mean and the truncated mean, it also forms the basis for robust measures of skewness and kurtosis, and even a normality test.

See also※

• Summary statistics
• Socio-economic decile (for New Zealand schools)

References※

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