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Statistical function
BETA.INV
Returns the inverse of the cumulative beta distribution.
Rarely usedDifficulty 1550 · AdvancedUsage rank #419 of 520
When to use it
The value of x at a given cumulative probability of the beta distribution. Credible intervals for a rate, PERT percentiles.
The shape of it
- Syntax
=BETA.INV(probability, alpha, beta, [A], [B])
Worked examples
Median
=BETA.INV(0.5,2,2) → 0.5
The median of a symmetric beta.
Round trip
=BETA.INV(0.26171875,2,3) → 0.25
Inverts the BETA.DIST example.
Uniform
=BETA.INV(0.95,1,1) → 0.95
Beta(1,1) is uniform, so percentiles are identity.
Worth knowing
- 95% credible interval for a rate: BETA.INV(0.025,s+1,f+1) to BETA.INV(0.975,s+1,f+1).
- A and B rescale to a task-duration range.
- Random beta values: BETA.INV(RAND(),alpha,beta).
Where it goes wrong
- #NUM! when probability is outside 0 to 1 or parameters are not positive.
- Uses an iterative search; extreme parameters can be slow.
Related
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