Decile
A decile is one of nine values that split ranked data into ten equal-sized groups of 10% each. Deciles locate an observation's relative position, such as income or fund-return rank.
What it is
See it move
Twelve stores' monthly revenue, in €'000, ranked: 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32. The seventh decile sits at position 7 × 13 ÷ 10 = 9.1, interpolating between the ninth value (26) and the tenth (28): D7 = 26 + 0.1 × 2 = 26.2. About seventy per cent of these stores' revenue falls below €26,200.
The formula
Variables
- k-th decile (rank position in ordered data)
- Decile number (1 to 9)
- Number of observations
Gives the (possibly fractional) rank position of the k-th decile among n ordered observations; interpolate between the two nearest values when the position is not a whole number.
Check yourself
A logistics firm times ten deliveries (in minutes), sorted: 5, 7, 8, 10, 11, 13, 14, 16, 18, 20. What is the third decile (D3) of delivery time?