How To Use BETADIST Function in Google Sheets

The BETADIST function in Google Sheets is useful when you need to compute the probability of a given value using the beta distribution function.

The beta distribution is commonly used to study variation in the percentage of something across samples.

The rules for using the BETADIST function in Google Sheets are as follows:

  • The function requires five arguments, which collectively define the beta distribution function to use and at what value to evaluate.
  • The function then outputs a number that corresponds to the cumulative beta probability.

Let’s take a look at a quick example! 

The beta distribution is really just a probability distribution on probabilities. For example, we can use it to model the probabilities of the success of a certain medical treatment, the effectiveness of a particular advertisement, or even how likely someone will live to a certain age.

For example, let’s say you would like to know the probability that you would be accepted to your preferred university. In this example, we can assume that probability can be modeled with a beta distribution where alpha is 2 and beta is 3. How can we know the probability that he has a greater than 50% chance of being accepted?

With the BETADIST function, it becomes quite easy to perform this calculation. We already have the alpha and beta values, as well as the value at which to evaluate the function (0.5).

We can use the BETADIST function to calculate all sorts of probabilities, ranging from applications in data science to even project management, where it is a key tool to understand the amount of time it will take to realistically finish a project. 

Let’s figure out how to write the BETADIST function ourselves in Google Sheets. Later, we’ll test out the function with actual values to see the formula in action.

 

 

The Anatomy of the BETADIST Function

The syntax of the BETADIST function is as follows:

=BETADIST(value, alpha, beta, lower_bound, upper_bound)

Let’s dissect this thing and understand what each of these terms means:

  • = the equal sign is how we start any function in Google Sheets.
  • BETADIST() is our BETADIST function. It returns the probability of a given value as defined by the beta distribution function.
  • value is the value at which to evaluate the probability function.
  • alpha refers to the first shape parameter of the distribution.
  • beta refers to the second shape parameter of the distribution.
  • lower_bound is the lower boundary of the function.
  • upper_bound is the upper boundary of the function.
  • The alpha and beta values must be a positive number.
  • The default lower and upper values are 0 and 1, respectively.

 

 

A Real Example of Using BETADIST Function

Let’s look into an example of the usage of BETADIST function in Google Sheets.

In the table below, we look at the beta distribution of our prior university example, which has an alpha of 2 and a beta of 3 at certain values. For example, there is a 68.75% chance of having at least a 50% chance of getting into his chosen university. Inversely, there is about a 31% chance that he has more than a 50% chance of getting accepted.

Using the BETADIST Function in Google Sheets

 

To get the values found in Column G, we just need to use the following formula:

=BETADIST(B2,C2,D2,E2,F2)

You can make a copy of the spreadsheet above using the link I have attached below. 

In this second example, let’s say that the lottery claims that at least one out of every 100 people wins. Of the last 1000 lottery tickets sold, 17 were winners. Based on this sample, can we compute the probability that there is at least a 1% probability of winning a ticket? 

Using the BETADIST distribution, we can compute the probability that the claim is true. Using the given values as arguments, we now know that the claim is very likely to be true.

Using BETADIST Function in Google Sheets to check probability

 

If you’re prepared to try out the BETADIST function in Google Sheets, let’s start writing it ourselves! The next section will guide you on how to ensure you’ve set up the BETADIST function correctly.

 

 

How to Use BETADIST Function in Google Sheets

  1. In this example, we’ll guide you through filling up column G, as seen in the example provided earlier. First, we should select cell G2, which will hold our BETADIST function.
    Select the cell to write the BETADIST function

  2. Next, we will then type the equal sign ‘=‘ to begin the function, followed by ‘BETADIST(‘. 
  3. As seen below, we can see a pop-up box that displays information on the function we just typed out in the Formula Bar. We can click on the arrow seen in the top-right-hand corner of the box to minimize it if needed.
    Typing the BETADIST function in the formula bar

  4. The next step is to type in our arguments in the proper order. Next, simply hit Enter on your keyboard to let the function evaluate.
    BETADIST function returns the beta distribution in percentages

  5. We can then drag down the formula to fill in the rest of the probabilities.
    Filling entire table with the formula

 

That’s all you need to start using the BETADIST function in Google Sheets. This step-by-step tutorial should show you how easy it is to find a certain probability using the beta distribution function.

You can use the BETADIST function in Google Sheets together with the various other Google Sheets formulas available to build great Google Sheets solutions yourself.

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