Survival function.

prob.py

from scipy.stats import chi2

def compare_chi2(first, second):
    """Given two dictionaries (usually simulated and actual), 
    return the survival probability"""
    if len(first['J2000']) != len(second['J2000']):
        raise Exception
    return chi2.sf(np.sum((second['da'] - first['da'])**2 / second['eda']**2.0), len(first['da']) - 1)

average = keck_error.copy()
average['da'] = np.ones_like(average['da'] * np.average(keck_error['da']))
compare_chi2(average, keck_error)