Decile

Template:Short description 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 $D_1$ to $D_9$ ($D_1$ = 10th percentile, $D_2$ = 20th percentile and so on). It is calculated as follows:

$DM=\frac{\sum _{i=1}^9{D}_i}{9}$

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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