Syntax
NORM.INV(probability, mean, standard_dev)
| Parameter | Description |
|---|---|
| probability | Parameter of the NORM.INV function. |
| mean | Parameter of the NORM.INV function. |
| standard_dev | Parameter of the NORM.INV function. |
Examples
Top 10% threshold
Formula
=NORM.INV(0.90, 500, 100)
Returns 628.2 — on a test with mean 500 and std dev 100, you need to score at least 628 to be in the top 10%.
Bottom 5% cutoff
Formula
=NORM.INV(0.05, 72, 8)
Returns 58.8 — scores below 59 fall in the bottom 5% of the distribution.
Z critical value
Formula
=NORM.INV(0.975, 0, 1)
Returns 1.96 — the z-value where 97.5% of the distribution lies below. This is the critical value used in 95% two-tailed confidence intervals.
Common Errors
#NUM!
Probability must be strictly between 0 and 1 (exclusive). Standard deviation must be positive.
#VALUE!
Non-numeric arguments.
Tips
Inverse of NORM.DIST
NORM.INV is the inverse of NORM.DIST with cumulative=TRUE. If NORM.DIST(x, m, s, TRUE)=p, then NORM.INV(p, m, s)=x.
Generate random normal values
=NORM.INV(RAND(), mean, stdev) generates a random value from a normal distribution. Useful for Monte Carlo simulations.
Setting grade boundaries
Use NORM.INV to set letter grade cutoffs. For example, the top 15% gets an A: =NORM.INV(0.85, class_mean, class_stdev) gives the minimum A score.
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