Percentiles and quartiles
Percentiles
Calculate the $p \in (0,1)$ percentile based on $L_p = p(n+1)$:
=PERCENTILE.EXC(data,p)
Note that Excel also provides =PERCENTILE.INC(data,p)
where $p \in [0,1]$ (i.e. the 0 or 1 are valid values for $p$.)
Quartiles
Calculate the $k \in [1,2,3,4]$ quartile:
=QUARTILE.EXC(data,k)