probability_to_significance_normal_limit

gammapy.stats.probability_to_significance_normal_limit(probability)

Convert tail probability to significance in the limit of small p and large s.

Reference: Equation (4) of http://adsabs.harvard.edu/abs/2007physics...2156C They say it is better than 1% for s > 1.6.

Asymptotically: s ~ sqrt(-log(p))