How this calculator works
Enter sample mean, sample standard deviation, sample size, critical z score. CalcStack applies the displayed formula and reports each intermediate planning value with the units shown.
Formula / method
Interval = mean ± z × standard deviation ÷ √n
Worked example
Mean 72, SD 12, n=100 and z=1.96 gives 69.648 to 74.352.
Assumptions and limitations
Observations are independent and the normal or large-sample approximation is appropriate.
For small samples with unknown variance, use a t critical value; sampling bias is not corrected.