Subjective De-Biasing of Data Sets: A Bayesian Approach

by M. Elisabeth Pat?-Cornell, Stanford Univ, Stanford, United States,



Document Type: Proceeding Paper

Part of: Risk-Based Decision Making in Water Resources VI

Abstract:

In this paper, we examine the relevance of data sets (for instance, of past incidents) for risk management decisions when there are reasons to believe that all types of incidents have not been reported at the same rate. Our objective is to infer from the data reports what actually happened in order to assess the potential benefits of different safety measures. We use a simple Bayesian model to correct (`de-bias') the data sets given the nonreport rates, which are assessed (subjectively) by experts and encoded as the probabilities of reports given different characteristics of the events of interest. We compute a probability distribution for the past number of events given the past number of reports. We illustrate the method by the cases of two data sets: incidents in anesthesia in Australia, and oil spills in the Gulf of Mexico. In the first case, the `debiasing' allows correcting for the fact that some types of incidents, such as technical malfunctions, are more likely to be reported when they occur than anesthetist mistakes. In the second case, we have to account for the fact that the rates of oil spill reports in different incident categories have increased over the years, perhaps at the same time as the rates of incidents themselves.

Subject Headings: Information management | Hazardous materials spills | Risk management | Probability | Bayesian analysis | Data analysis | Probability distribution | Australia | Gulf of Mexico

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