Sort the data from smallest to largest
Find the position using the formula: `P = (n + 1) × (percentile / 100)`
If `P` is a whole number, the percentile is the value at that position
If `P` is not a whole number, interpolate between the two surrounding values
For interpolation, use: `lower value + decimal part × (upper value – lower value)`
Example: for the 25th percentile in 20 values, compute `P = (20 + 1) × 0.25 = 5.25`
Use the 5th and 6th values
Compute: `5th value + 0.25 × (6th value – 5th value)`