Lawrence Berkeley National Laboratory (LBNL), Mar. 2017, by Mark Bolinger.
https://emp.lbl.gov/sites/default/files/lbnl-1007269.pdf

"This paper presents a new framework, grounded in statistical concepts related to probability of exceedance (and confidence intervals more broadly), to incorporate resource risk into decision-making processes. This framework recognizes that the same probability of exceedance concepts that are regularly used to characterize the uncertainty around annual energy production for wind and solar projects can also be applied to natural gas price projections, allowing one to develop a probabilistic range of projections for not only wind and solar capacity factors, but also natural gas prices."