The computation of these partition values is done exactly in the same manner as the computation of the Median. In a series of individual observations and in a discrete series, the values of the lower (Q1) and the upper (Q9) quartiles would be the value of (N+1) /4) th and (3(N+1) / 4 items respectively.
The values of the deciles in such series would be as follows.
The values of the percentiles would be In continuous series in the calculation of quartiles, deciles and percentiles (N+1)/4 , (N+1)/10 and (N+1)/100 would be replaced by N/4 ,N/10 and N/100 respectively. The values would have to be interpolated here as was done in case of the computation of Median.