How this calculator works
Enter value x, mean μ, standard deviation σ. CalcStack applies the displayed formula and reports each intermediate planning value with the units shown.
Formula / method
P(X≤x) = ½[1 + erf((x−μ) ÷ (σ√2))]
Worked example
x=75, mean 60 and SD 10 gives z=1.5 and cumulative probability about 93.32%.
Assumptions and limitations
The variable is adequately modeled by a normal distribution.
Normality, outliers, discrete values and parameter uncertainty are not tested.