Cumulative probability graphs

Cumulative probability graphs rank the data in a simulation from the highest to the lowest value, and graph each point with its corresponding percentile. Upward sloping cumulative probability graphs indicate the proportion of data in a simulation predicted below each value on the x-axis. Downward sloping cumulative probability graphs indicate the proportion of data in a simulation predicted to exceed each value on the x-axis.

To analyse simulations using cumulative probability graphs:

1. Open the [Charts] menu and select [Probability…],
   …or click on the icon on the toolbar.
2. Select the data for analysis in the Probability form. Choose the simulation(s) you wish to analyse in the upper selection window, and the data you wish to analyse in the lower window.
3. Choose whether to view Probability of exceedence (downward sloping) or Cumulative probability (upward sloping) distributions.

Probability of exceedence graphs show the probability of a simulation exceeding a particular value. The slope is downwards because there is a high probability that yield will exceed low values, and a low probability that yield will exceed high values.

Cumulative probability graphs show the probability that a simulation will be less than a particular level. They slope upwards because there is a low probability of yield being less than low values and a high probability of yield being less than high values.