The BETADIST function in Excel is used to calculate the cumulative beta probability density function. However, keep in mind that BETADIST was replaced with the BETA.DIST function in Excel 2010 and later versions, although BETADIST is still available for compatibility reasons.
Here’s how to use the BETADIST function:
Syntax for BETADIST
BETADIST(x, alpha, beta, [A], [B])
- x: The value between A and B at which to evaluate the function.
- alpha: A parameter of the distribution. Must be greater than 0.
- beta: Another parameter of the distribution. Must be greater than 0.
- A (optional): The minimum value of the interval of x. If omitted, A defaults to 0.
- B (optional): The maximum value of the interval of x. If omitted, B defaults to 1.
Example
Suppose you want to evaluate the beta distribution at a point `x`, with parameters `alpha`, `beta`, `A`, and `B`.
Let’s say:
- `x` = 0.5
- `alpha` = 2
- `beta` = 5
- `A` = 0
- `B` = 1
The function would be set up in Excel as follows:
=BETADIST(0.5, 2, 5, 0, 1)
Note:
- Parameters: Ensure that `x` is between `A` and `B`, and both `alpha` and `beta` are greater than 0.
- Old vs New Function: If you’re using a version of Excel that supports BETA.DIST (Excel 2010 and later), it’s recommended to use this updated function as it offers both the cumulative distribution and the probability density function, depending on an additional logical parameter.
Modern Equivalent (BETA.DIST)
In more recent versions of Excel, you should use BETA.DIST:
=BETA.DIST(x, alpha, beta, cumulative, [A], [B])
- cumulative: A logical argument (TRUE for the cumulative distribution function, FALSE for the probability density function).
This function provides enhanced functionality and is aligned with Excel’s current suite of statistical functions.
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