Myron B Fiering

Resilience of a statistical sampling scheme

Abstract Most statistical sampling algorithms on hydrologic random fields assume that the new measurements will agree reasonably well with their predicted values. This in turn implies the stationarity of the estimated covariance function. In order to test the reliability of one such statistical algorithm (i.e., variance reduction analysis), noisy input data are generated, and results of sampling from these data are compared to the case of sampling with the unperturbed data. These comparisons and a related regret analysis reveal that the effects of the noisy data are primarily accommodated by adjustments to the covariance function parameters, while selected sets show a high degree of resilience. Variance reduction analysis seems to be a reliable method for maximizing information by sampling random fields with an unstable parameter space but a resilient action space.

Prioritization of chemical carcinogenesis testing: the use of production data

Abstract Based on previous work, this paper aims to show how approximate methods of estimating exposure can lead to a preliminary ranked list of chemicals for regulation of carcinogens. This list is likely to be more reliable, than those so far generated. The paper argues four main points. Firstly that an indication of the route by which the total production of a hazardous material is distributed and enters the human body should be explicitly included in calculations. Second, simple calculations based on conservative bounds should be made to establish a ranking or set of priorities for regulation. Third, an improved system for establishing regulatory priorities can be based on formal analysis using regret functions. Finally some simple, bounded, calculations based on commonly used herbicides and pesticides are made and it is shown how some regulatory processes could be modified.

A DIGITAL COMPUTER SOLUTION FOR WELL FIELD DRAW-DOWN

Abstract A numerical approximation to the solution of Darcys equation for flow in a porous medium is coded for solution on a digital computer. Non-steady pumping and recharge rates, generalized well patterns, and varying aquifer characteristics are accounted for by the solution. Sample computations are presented.

Analysis of disclosure avoidance procedures

Abstract In the collection of data on environmental health, individuals are frequently reluctant to be entirely candid with surveyors because of concern over the confidentiality of responses. A standard procedure is to inoculate the response with random modification (or error) so that it becomes impossible to identify individual respondents but quite possible to generate unbiased statistical summaries of the entire sample. This paper is directed at generating methods for such random inoculation and abstracting from the inoculated results those conclusions concerning sample response and population estimates. A numerical example of a bivariate randomized procedure is given.