Syntax
BETA.DIST(x, alpha, beta, cumulative, [A], [B])
| Parameter | Description |
|---|---|
| x | Parameter of the BETA.DIST function. |
| alpha | Parameter of the BETA.DIST function. |
| beta | Parameter of the BETA.DIST function. |
| cumulative | Parameter of the BETA.DIST function. |
| [A] | (Optional.) Parameter of the BETA.DIST function. |
| [B] | (Optional.) Parameter of the BETA.DIST function. |
Examples
Bayesian probability estimate
Formula
=BETA.DIST(0.3, 5, 15, TRUE)
Returns ~0.7216. After observing 4 successes and 14 failures (prior + data), there is about a 72% probability that the true conversion rate is 0.3 or lower.
PERT project timeline
Formula
=BETA.DIST(12, 2, 3, TRUE, 8, 20)
Returns ~0.4069. In a PERT analysis with optimistic=8 and pessimistic=20 days, there is about a 41% chance of completing within 12 days.
PDF of a proportion
Formula
=BETA.DIST(0.5, 2, 5, FALSE)
Returns ~1.875. The probability density at p=0.5 when the beta parameters are alpha=2, beta=5. The peak of this distribution is around 0.2.
Common Errors
#NUM!
x must be between A and B (default 0 and 1). Alpha and beta must be positive. If A >= B, this error occurs.
#VALUE!
Occurs when arguments are non-numeric.
Tips
Alpha and beta interpretation
Think of alpha as 'number of successes + 1' and beta as 'number of failures + 1' in a Bayesian context. Higher values mean more data and a tighter distribution.
Optional bounds A and B
By default the beta distribution covers [0,1]. Set A and B to rescale it to any interval, useful for PERT estimates and bounded physical quantities.
A/B testing application
After an A/B test with s successes and f failures, the posterior distribution of the true rate is Beta(s+1, f+1). Use BETA.DIST to compute probabilities about that rate.
Try BETA.DIST in Viztab
Import your data and use BETA.DIST with 370+ other formulas. No signup required.
Open Viztab