F test with python, finding the critical value
Question: Using python, Is it possible to calculate the critical value on F distribution
with x and y degrees of freedom? In other words, I need to calculate the
critical value given a x degrees of freedom and a confidence level 5%, but i
do not see the table from statistical books, is it posible to get it with any
function from python?

For example, I want to find the critical value for a F distribution with 3 an
39 degrees of freedom for 5% of confidence level. The answer should be: 2.85


Answer: IIUC, you can use
[`scipy.stats.f.ppf`](http://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.f.html),
which gives the inverse of the cdf:

    
    
    >>> import scipy.stats
    >>> scipy.stats.f.ppf(q=1-0.05, dfn=3, dfd=39)
    2.8450678052793514
    >>> crit = _
    >>> scipy.stats.f.cdf(crit, dfn=3, dfd=39)
    0.95000000000000007
    

