The Python Calculator filter allows you to use the function median, which is included in numpy.
Indeed, the median can be calculated by typing the following in the Expression field of the Python Calculator. (Note that there is a bug if the variable name contains a slash, so the variable call is more redundant than usual.)
np.median(inputs[0].CellData['Resistivity/Ohmm'])
The calculated median may be viewed in Spread Sheet View, for example.