The chance that a deal at a given stage is eventually won, measured from closed deals or, more often, left at a CRM default.
Stage probability is the weight applied to a deal in a weighted pipeline. Measured properly it is, per stage, deals that reached the stage and were won over deals that reached it and were decided, over the trailing four quarters, with stalled deals counted as lost. In most CRMs it is a default nobody tested, and the measured figures usually differ from the defaults by twenty points or more at late stages. See pipeline coverage versus weighted pipeline.
For each stage, deals that reached it and were won divided by deals that reached it and were decided, over four quarters, with stalled deals counted as lost.
The CRM default for proposal is 60 percent. Measured on the team's own deals it is 35.
Defaults used. Weighted pipeline is then an exact-looking figure built on five numbers nobody tested.