# Overview of a Probabilistic Analysis

In a Probabilistic analysis, you can define statistical distributions for input parameters (e.g. joint orientation, shear strength, water level), to account for uncertainty in the values of input parameters. When the analysis is computed, this results in a safety factor distribution from which a probability of failure (PF) is calculated.

The general procedure for carrying out a Probabilistic Analysis with **SWedge** is as follows.

#### Select Analysis Type

Set the Analysis Type to

**Probabilistic**in the Project Settings dialog.#### Set Sampling Options

In the

**Project Settings**dialog you can choose the Sampling Method, Number of Samples, and Random Numbers options.#### Define Random Variables

In order to carry out a Probabilistic analysis, you must define one or more input parameters (e.g. joint orientation, shear strength) as random variables, by assigning statistical distributions to the desired variables and entering the required statistical parameters (e.g. mean, standard deviation). See the Random Variables topic for a summary of the random variables which can be defined in

**SWedge**.**NOTE:**Any input parameter which is NOT assigned a Statistical Distribution, is assumed to be exactly known (by the Mean value), and will not be involved in the statistical sampling process.#### Compute

The Probabilistic analysis is computed when you select OK (or Apply) in the Input Data dialog. You can also select the Compute option in the toolbar.

#### View Analysis Results

After the analysis is computed, the Sidebar will display a summary of results (probability of failure, mean safety factor etc). Probabilistic input and output data can be plotted on Histogram plots, Scatter plots etc. Data can also be exported for further analysis and processing.