In descriptive statistics , using the percentile is a way of providing estimation of proportions of the data that should fall above and below a given value. The p th percentile is a value such that at most (100 p )% of the observations are less than this value and that at most 100(1 - p )% are greater. (p is a value between 0 and 1)
- The 1st percentile cuts off lowest 1% of data
- The 98th percentile cuts off lowest 98% of data
The 25th percentile is the first quartile ; the 50th percentile is the median .
One definition is that the pth percentile of n ordered values is obtained by first calculating the rank , rounded to the nearest integer and then taking the value that corresponds to that rank. One alternative method, used in many applications, is to use a linear interpolation between the two nearest ranks instead of rounding.
Linked with the percentile function, there is also a weighted percentile, where the percentage in the total weight is counted instead of the total number. In most spreadsheet applications there is no standard function for a weighted percentile.
Relation between percentile, decile and quartile
1.) P25 = Q1
2.) P50 = D5 = Q2
3.) P75 = Q3
4.) P100 = D10 = Q4
5.) P10 = D1
6.) P20 = D2
7.) P30 = D3
8.) P40 = D4
9.) P60 = D6
10.) P70 = D7
11.) P80 = D8
12.) P90 = D9
Note: One quartile is equivalent to 25 percentile while 1 decile is equal to 10 percentile.