Percentiles (100 regions)
The kth percentile is the number which has k% of the values below it. The data must be ranked.
- Rank the data
- Find k% (k /100) of the sample size, n.
- If this is an integer, add 0.5. If it isn't an integer round up.
- Find the number in this position. If your depth ends in 0.5, then take the midpoint between the two numbers.
It is sometimes easier to count from the high end rather than counting from the low end. For example, the 80th percentile is the number which has 80% below it and 20% above it. Rather than counting 80% from the bottom, count 20% from the top.
Note: The 50th percentile is the median.
If you wish to find the percentile for a number (rather than locating the kth percentile), then
- Take the number of values below the number
- Add 0.5
- Divide by the total number of values
- Convert it to a percent
