Decile

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^th percentile, ${\displaystyle D_{2}}$ = 20^th percentile and so on). It is calculated as follows:^[3]

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

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.^[4]

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