Math387.NormalQuantile Method

function NormalQuantile(p: Double): Double;

Normal (Gaussian) quantile, the inverse of the standard normal CDF.

#NameTypeDescription
1pDoublescalar

Returns: Double - z such that the standard normal CDF at z equals p.

Remarks:

Shares the ALGORITHM AS241 (PPND16) rational approximations with Math387.ErfInv, but takes the probability p directly. Prefer this over SQRT2*ErfInv(2*p-1): forming 2*p-1 caps the tail mass at an absolute 5.55E-17, which costs about 1.1E-12 relative accuracy at p=1E-6 and returns -MAXNUM for p below roughly 1E-17. Returns 0 outside 0 < p < 1.

See Also: Math387.ErfInv