Sort the data from smallest to largest
Find the position using: ( P = frac{p}{100} times (n + 1) )
If the position is a whole number, take the value at that position
If the position is not a whole number, interpolate between the two nearest values
For the kth percentile, use ( p = k )
For the median, use the 50th percentile
For the first quartile, use the 25th percentile
For the third quartile, use the 75th percentile
If using a calculator or software, follow its percentile method because formulas may differ