P50 (and P90, Mean, Expected and P10) is the methodology based on simulating potential scenarios with Monte Carlo Simulations, where the P stands for Percentile. In the oil and gas industry, P90 should be at least a 90% probability that the quantities actually recovered will equal or exceed the low estimate; P50 should be at least a 50% probability that the quantities actually recovered will equal or exceed the best estimate; P10 should be at least a 10% probability that the quantities actually recovered will equal or exceed the high estimate. P50 is a good middle estimate, mean and expected.
Related Definitions in the Project: The Project Management
