In Layman terms continuous probability distribution is known as the Weibull distribution and it is widely used in statistics to obtain a model for several data sets, the original formula to calculate Weibull distribution is very complex but we have an inbuilt function in excel known as Weibull.Dist function which calculates Weibull distribution.
Weibull Distribution in Excel (Table of Contents)
- Weibull Distribution in Excel
- Explanation of Weibull Distribution in Excel
- How To Use Weibull Distribution in Excel?
Weibull Distribution in Excel (WEIBULL.DIST)
Before we begin to move towards the topic of Weibull distribution we need to know what a probability distribution is. As by the definition goes, Weibull distribution is a continuous probability distribution.
The probability distribution is a function in mathematics which calculates the occurrence of different possible outcomes of a phenomenon. The continuous probability distribution is based on outcomes which take a possible set of outcomes from real numbers. For example, If we have to predict the probability of the wind density of the weather we use continuous probability distribution. Let us have a look below how the mathematical Weibull Distribution formula looks like,
As we can see that on the left-hand side there are three variables: x, Lambda, and K. Now there are certain rules for these variables. X, Lambda and k cannot be zero else we will have an inaccurate value.
The above equation was a mathematical function. We have a Weibull distribution function (WEIBULL.DIST) built in excel which looks like the below screenshot,
X alpha and beta are the numbers given for input while cumulative is the logical argument true or false.
Explanation of Weibull Distribution in Excel (WEIBULL.DIST)
We have already learned that Weibull distribution is a continuous probability distribution. And Weibull distribution function in excel of two types:
- Weibull Cumulative Distribution Function
- Weibull Probability Density Function
The only difference between the two types of Weibull distribution function is the cumulative logical argument,
Weibull Cumulative Distribution Function takes True as a cumulative argument whereas Weibull Probability Density Function takes False as a cumulative argument.
How To Use Weibull Distribution in Excel?
To use Weibull distribution we need to have three values which are X, Alpha, And Beta.
- X is a value to the function.
- Alpha is a parameter to the function.
- Beta is also a parameter to the function.
- Cumulative is a logical argument which can be either true or false depending upon the type of Weibull distribution function we are trying to use. If we are using Weibull Cumulative Distribution Function then the cumulative value will be true or we are using Weibull Probability Density Function then the cumulative value will be false.
Let us learn the Weibull distribution in excel by a few examples.
Example #1 – Weibull Cumulative Distribution Function
AS we know X is valued at which we evaluate the function, Alpha & Beta both are the parameters to the function. Let us use this function in excel.
Step#1 – Give value to the WEIBULL.DIST function, for example, 100
Step#2 – Now let us give the parameter to the function i.e. Alpha and Beta.
Step#3 – In the Weibull Distribution Box, Type
Step#4 – Press the Tab button and click on the Fx function button.
Step#5 – A dialog box pops up.
Step#6 – In the Box for X select the value against the value to the function.
Step#7 – For the parameter to the function, select the value for alpha and beta,
Step#8 – Cumulative is a logical value which can be either true or false and both have a different meaning. Let us insert true first.
Step#9 – Click on and we get the result for Weibull distribution.
The above value calculate is Weibull Cumulative Distribution. To get this the value of cumulative should be true.
Example #2 – Weibull Probability Density Function
We have seen that Inserting True in the value of cumulative gives us Weibull Cumulative Distributive Value. If we insert False at the cumulative it gives us Weibull Probability Density Value. Let us go with the first example.
We have seen that X is valued at which we evaluate the function, Alpha & Beta both are the parameter to the function. Let us again use this function in excel.
Step#1 – We will again give a value to the function, i.e. 190 for this case.
Step#2 – Now we give a parameter to the function which is alpha and beta,
Step#3 – Now in the Weibull distribution box type,
Step#4 – Press Tab and click on Fx function bar,
Step#5 – A dialog box appears for the function arguments,
Step#6 – Now we will give the value of the function and value of the parameters i.e. Alpha and Beta.
Step#7 – Previously We inserted True as the value in cumulative now we will insert False as a value in the cumulative logical value.
Step#8 – Click on OK and we will get our desired value.
The value above calculated is Weibull Probability Density.
Things to Remember about Weibull Distribution in Excel
There are a few things to remember about Excel Weibull Distribution:
- X which is a value to the function is a non-negative number and cannot be zero, so it should be greater than zero.
- Alpha And Beta which are the parameter to the function the also need to be equals to or greater than zero.
- We get two types of errors in Excel Weibull Distribution.
- #NUM!: This error comes when the value of x is less than zero.
- #Value!: This error comes if any arguments given is non-numeric.
This has been a guide to Weibull distribution in Excel. Here we discuss how to use WEIBULL.DIST Function along with practical examples and downloadable Excel template. You may learn more about excel from the following articles –
- Examples of Poisson Distribution Formula
- Explanation of the Hypergeometric Distribution Formula
- Calculation of Beta in Finance
- What is Binomial Distribution Formula?
- Lognormal Distribution Excel
- NORMDIST in Excel
- NORM.S.INV Function
- What is Descriptive Statistics in Excel?
- How to use Exponential Smoothing in Excel