Syntax
BETADIST(x, alpha, beta, [A], [B])
| Parameter | Description |
|---|---|
| x | Parameter of the BETADIST function. |
| alpha | Parameter of the BETADIST function. |
| beta | Parameter of the BETADIST function. |
| [A] | (Optional.) Parameter of the BETADIST function. |
| [B] | (Optional.) Parameter of the BETADIST function. |
Examples
Probability proportion is below 0.4
Formula
=BETADIST(0.4, 3, 7)
Returns ~0.8328. With alpha=3 and beta=7, there is about an 83% probability the true proportion is 0.4 or lower.
Bounded variable estimate
Formula
=BETADIST(15, 2, 4, 10, 25)
Returns ~0.4553. For a variable bounded between 10 and 25, there is about a 46% chance it falls at or below 15.
Uniform distribution check
Formula
=BETADIST(0.5, 1, 1)
Returns 0.5. With alpha=beta=1, the beta distribution is uniform on [0,1], so the CDF at 0.5 is exactly 0.5.
Common Errors
#NUM!
x must be between A and B (default 0 and 1). Alpha and beta must be positive.
#VALUE!
Occurs when arguments are non-numeric.
Tips
Always cumulative
BETADIST always returns the CDF. For the PDF, use BETA.DIST with cumulative=FALSE.
Use BETA.DIST instead
BETADIST is the compatibility function. BETA.DIST offers the additional PDF option and is the modern standard.
Symmetric when alpha = beta
When alpha equals beta, the distribution is symmetric around 0.5 (or the midpoint of [A,B]). The distribution becomes U-shaped when both are less than 1.
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