How to Use the WEIBULL.DIST Function in Excel

When working with data in spreadsheet applications such as Microsoft Excel and Google Sheets, the WEIBULL.DIST function is incredibly beneficial. This function is primarily used in reliability engineering for modeling product life expectancy through the Weibull distribution. This distribution is notably versatile since it can assume various forms based on its parameters.

Syntax

The syntax for the WEIBULL.DIST function is slightly different in Excel compared to Google Sheets:

Excel:

WEIBULL.DIST(x, alpha, beta, cumulative)

• x: The value at which the function is evaluated.
• alpha: The shape parameter of the distribution.
• beta: The scale parameter of the distribution.
• cumulative: A Boolean value that specifies the function’s mode. If cumulative is TRUE, WEIBULL.DIST returns the cumulative distribution function; if FALSE, it returns the probability density function.

Google Sheets:

WEIBULL.DIST(x, alpha, beta, cumulative)

The parameters in Google Sheets are identical to those in Excel.

Examples

Here are some practical examples to demonstrate the applications of the WEIBULL.DIST function.

Example 1: Calculate the Probability of a Product Failing Before a Certain Time

Suppose you have a product with a Weibull distribution where the shape parameter α=2 and scale parameter β=100. You wish to determine the probability that this product will fail before reaching 120 units of time.

In Excel, the formula is:

=WEIBULL.DIST(120, 2, 100, TRUE)

The same formula applies in Google Sheets:

=WEIBULL.DIST(120, 2, 100, TRUE)

This formula yields the cumulative distribution function at x=120, revealing the probability of failure before reaching 120 units of time.

Example 2: Generate a Weibull Probability Density Plot

To visualize the Weibull distribution for a shape parameter of α=1.5 and a scale parameter of β=50, you can plot the probability density function across a range of values.

In Excel, you can establish a table with various x values and apply the formula:

=WEIBULL.DIST(A2, 1.5, 50, FALSE)

Extend this formula across the table to compute the probability density function at different points, then use this data to plot a line chart representing the distribution.

Similarly, in Google Sheets:

=WEIBULL.DIST(A2, 1.5, 50, FALSE)

Extend the formula as needed and generate a chart to visualize the Weibull distribution.

In conclusion, the WEIBULL.DIST function is a robust tool for both modeling and analyzing Weibull distribution data in Excel and Google Sheets. It is essential for calculating probabilities or creating detailed visualizations, enabling efficient data handling specific to Weibull distributions.

More information: https://support.microsoft.com/en-us/office/weibull-dist-function-4e783c39-9325-49be-bbc9-a83ef82b45db