Vertaile menetelmiä

	Probabilistic Risk Assessment (PRA)	Vikapuuanalyysi (FTA)
Tieteenala	Disaster Studies	Luotettavuus
Menetelmäperhe	Process / pipeline	Process / pipeline
Syntyvuosi	1981	1981
Kehittäjä	Kaplan & Garrick (risk triplet); Rasmussen WASH-1400; codified in NASA PRA Guide	Vesely et al. (US NRC Fault Tree Handbook)
Tyyppi	Scenario-based quantitative risk model with uncertainty	Deductive top-down failure analysis
Alkuperäislähde	Stamatelatos, M., Dezfuli, H., et al. (2011). Probabilistic Risk Assessment Procedures Guide for NASA Managers and Practitioners (2nd ed.), NASA/SP-2011-3421. NASA, Washington, DC.	Vesely, W. E., Goldberg, F. F., Roberts, N. H., & Haasl, D. F. (1981). Fault Tree Handbook (NUREG-0492). U.S. Nuclear Regulatory Commission.
Rinnakkaisnimet	Probabilistic Safety Assessment, PSA, Quantitative Risk Assessment (PRA), Probabilistic Risk Analysis	FTA, Fault Tree Method, Top-Down Reliability Analysis, Hata Ağacı Analizi
Liittyvät	3	3
Tiivistelmä	Probabilistic Risk Assessment is the comprehensive, quantitative method for analyzing risk in complex engineered systems by answering three questions: what can go wrong, how likely is it, and how bad would it be. Kaplan and Garrick's 1981 paper gave the field its enduring definition of risk as a set of triplets — scenario, frequency, and consequence — and showed how to extend that definition to incorporate uncertainty through probability distributions. The NASA Probabilistic Risk Assessment Procedures Guide (NASA/SP-2011-3421) operationalizes this framework for high-consequence aerospace systems, combining initiating-event analysis, event trees and fault trees, consequence modeling, and formal uncertainty propagation into an integrated assessment. Unlike qualitative hazard identification, PRA produces a quantified risk picture — typically a frequency-of-exceedance curve with explicit uncertainty bounds — that supports decisions about where scarce safety resources will reduce risk most.	Fault Tree Analysis (FTA) is a top-down, deductive reliability method that begins with an undesired top-level failure event and systematically traces backward through chains of contributing causes using Boolean logic gates (AND, OR). First formalized by Watson at Bell Telephone Laboratories in 1961 and later standardized by Vesely, Goldberg, Roberts, and Haasl in the landmark 1981 NRC Fault Tree Handbook, FTA has become a cornerstone of quantitative risk assessment in nuclear, aerospace, and industrial safety engineering.