Hi Pratik,
PyFerret should add those statistic functions if it is able to import the scipy package. What you describe sounds like it was not able to import the scipy package in the version of Python that is running PyFerret. You might try running 'pyferret -python' (or run pyferret as usual and then enter the Ferret command 'EXIT /TOPYTHON') to get to the Python prompt. Then try 'import scipy' and 'import scipy.stats' to make sure it was able to find SciPy and its stats package, in that version of Python.
Best regards,
Karl