# GAMMA.INV

The `GAMMA.INV` formula returns the inverse of the cumulative distribution function for a specified probability and the Gamma distribution. It is commonly used in statistical analysis to find the value at which a specified percentage of the distribution lies. The Gamma distribution is a continuous probability distribution that is used to model the time until a certain number of events occur.

## Usage

Use the `GAMMA.INV` formula with the syntax shown below, it has 3 required parameters:

Parameters:
1. probability (required):
The probability for which to calculate the inverse cumulative distribution function.
2. alpha (required):
The shape parameter of the Gamma distribution.
3. beta (required):
The scale parameter of the Gamma distribution.

## Examples

Here are a few example use cases that explain how to use the `GAMMA.INV` formula in Google Sheets.

### Calculate the time until a certain number of events occur

The `GAMMA.INV` formula can be used to determine the time until a certain number of events occur when modeling a system with a Gamma distribution.

### Calculate the probability of an event occurring within a certain time frame

The `GAMMA.INV` formula can be used to determine the probability of an event occurring within a certain time frame when modeling a system with a Gamma distribution.

### Predict wait times for customer service calls

The `GAMMA.INV` formula can be used to predict wait times for customer service calls by modeling the time between calls with a Gamma distribution.

## Common Mistakes

`GAMMA.INV` not working? Here are some common mistakes people make when using the `GAMMA.INV` Google Sheets Formula:

### Misuse of probability argument

Users often input a probability value outside the range of 0 to 1. The probability argument must be a decimal value between 0 and 1.

### Incorrect order of alpha and beta arguments

Users sometimes mix up the order of the alpha and beta arguments. The correct syntax is GAMMA.INV(probability, alpha, beta).

### Invalid alpha or beta value

Users may input a negative value for alpha or beta. Both the alpha and beta values must be positive.

The following functions are similar to `GAMMA.INV` or are often used with it in a formula:

• `GAMMA`

The GAMMA function returns the Gamma function evaluated at the input value. The Gamma function is a commonly used function in mathematics, and is used in many statistical calculations. It is defined as the integral of t^(x-1)*e^(-t) from 0 to infinity. The GAMMA function can be used to calculate probabilities of certain events in statistical distributions.

• `GAMMALN`

The `GAMMALN` function returns the natural logarithm of the absolute value of the Gamma function, Γ(x). The Gamma function is defined as an extension of the factorial function to complex and real numbers. The function is commonly used in probability theory and statistics to compute probabilities and to model continuous distributions such as the chi-squared and F distributions.

• `GAMMALN.PRECISE`

The `GAMMALN.PRECISE` function calculates the natural logarithm of the absolute value of the gamma function for a given positive number. The gamma function is a commonly used function in mathematics and statistics. The natural logarithm of the gamma function is useful in various fields, such as physics, biology, and engineering, for modeling various phenomena.

• `GAMMA.DIST`

The GAMMA.DIST function calculates the gamma distribution probability for a specified x value, alpha and beta parameters. This function is often used in statistics to model continuous data that is skewed to the right. It can be used to analyze data in various fields such as finance, engineering, and social sciences.

You can learn more about the `GAMMA.INV` Google Sheets function on Google Support.