[SciPy-dev] scipy.stats: sf for symmetric distributions.

[David Warde-Farley]

On 16-Sep-09, at 3:53 PM, David Warde-Farley wrote:

> incidentally, this breaks two
> ttest tests because they differ in the 17th decimal place, how sure
> are you of those hard-coded numbers?).

I just did the integral with Sage and requested 100 bits of precision,  
more than we need, and got

sage: thepdf
1/4*sqrt(2)/(1/2*x^2 + 1)^(3/2)
sage: n(2 * integral(thepdf, x, -infinity, -1), prec=100)
0.42264973081037423549085121950


And in IPython:

In [92]: np.float64(0.42264973081037423549085121950)
Out[92]: 0.42264973081037421

So it seems that ...21 is the right answer and the hardcoded ...27 is  
actually the result of roundoff, it would seem.

I've fixed the tests.

David