You can try this:
this should be from Peter J. Acklam’s algorithm.
/* Put this in, say, the Text property of a Label (or wherever you need it).
Replace with your probability value (0<p<1).
With(
{
p: ProbabilityValue, //you can pass for example value from TextInput
p_low: 0.02425, /* split-points */
p_high: 0.97575,
/* coefficients for central region */
a1: -3.969683028665376E+01, a2: 2.209460984245205E+02,
a3: -2.759285104469687E+02, a4: 1.383577518672690E+02,
a5: -3.066479806614716E+01, a6: 2.506628277459239E+00,
b1: -5.447609879822406E+01, b2: 1.615858368580409E+02,
b3: -1.556989798598866E+02, b4: 6.680131188771972E+01,
b5: -1.328068155288572E+01,
/* coefficients for tails */
c1: -7.784894002430293E-03, c2: -3.223964580411365E-01,
c3: -2.400758277161838E+00, c4: -2.549732539343734E+00,
c5: 4.374664141464968E+00, c6: 2.938163982698783E+00,
d1: 7.784695709041462E-03, d2: 3.224671290700398E-01,
d3: 2.445134137142996E+00, d4: 3.754408661907416E+00
},
/* guard against p=0 or 1 */
If(
p <= 0,
-1e10,
If(
p >= 1,
1e10,
/* now the 3 regions */
If(
p < p_low,
/* lower tail */
With(
{ q: Sqrt(-2 * Ln(p)) },
-(
(((( (c1 * q + c2) * q + c3) * q + c4) * q + c5) * q + c6)
/
(((( (d1 * q + d2) * q + d3) * q + d4) * q + 1))
)
),
If(
p <= p_high,
/* central region */
With(
{ q: p - 0.5, r: (p - 0.5) * (p - 0.5) },
(
(((( (a1 * r + a2) * r + a3) * r + a4) * r + a5) * r + a6)
* q
)
/
(
(((( (b1 * r + b2) * r + b3) * r + b4) * r + b5) * r + 1)
)
),
/* upper tail */
With(
{ q: Sqrt(-2 * Ln(1 - p)) },
(
(((( (c1 * q + c2) * q + c3) * q + c4) * q + c5) * q + c6)
/
(((( (d1 * q + d2) * q + d3) * q + d4) * q + 1))
)
)
)
)
)
)
)
Share
Report
260
All responses (
Answers (
