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In this article
NORM.S.INV returns the z-score for a cumulative probability — where the famous 1.96 comes from.
Syntax
=NORM.S.INV(probability)| Argument | What it means |
|---|---|
probability |
Between 0 and 1. |
Examples
Example 1
=NORM.S.INV(0.975)About 1.96.
Example 2
=NORM.S.INV(0.95)About 1.645, the z for 95% service level in safety-stock formulas.
NORM.S.INV in practice
Where you will use it
- z for a confidence level
- Critical values
- Sample size calculations
Worked example
| Probability | Formula | Result |
|---|---|---|
| 0.975 | =ROUND(NORM.S.INV(A2),4) | 1.96 |
| 0.95 | =ROUND(NORM.S.INV(A3),4) | 1.6449 |
| 0.5 | =ROUND(NORM.S.INV(A4),4) | 0 |
Results calculated in Excel.
Mistakes people make
| Mistake | What to do instead |
|---|---|
| Two-tailed 95% | Use 0.975, not 0.95 |
| Range | Only between 0 and 1 |
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