For reference, 6 sigma is one-in-a-billion case (one-tail): print(f"{1 - statistics.NormalDist().cdf(6):.1g}") # 1e-09 and 2 sigma is two-in-a-hundred

For reference, 6 sigma is one-in-a-billion case (one-tail): print(f"{1 - statistics.NormalDist().cdf(6):.1g}") # 1e-09 and 2 sigma is two-in-a-hundred (~2%). ~5% for two-tail case.