Jim, of the two often-cited certainties of death and taxes, I have thought that the certainty of taxes could be changed. I can dream.
To those two certainties of death and taxes, I wish to add the certainty of empty soap dispensers in public toilets---or so it seems. Paul Trusten, R.Ph. Registered Pharmacist Vice President and Public Relations Director U.S. Metric Association, Inc. Midland, Texas US www.metric.org +1(432)528-7724 trus...@grandecom.net On Mar 17, 2011, at 20:20, "James R. Frysinger" <j...@metricmethods.com> wrote: > An obstreperous reporter at today's White House press conference and a news > commentator I watched and listened to this afternoon have reminded me that > most folks do not understand what is meant by "safety", "safety limit", etc. > Most folks think things are safe or are not safe -- a rather binary (0 or 1) > understanding, that is, 0 % risk or 100 % of ill effects. But in the real > world, "safety" must be qualified by weak statistics -- odds, if you will. > > The obnoxious reporter and the news commentator were stumped when Japan told > people within 20 km (12 miles) of the reactors to leave and the U.S. told > American citizens within 50 miles to leave the area. Both "inquiring minds" > wanted to know, "Which is it -- 12 miles or 50 miles?" The answer, which the > WH spokesman (Director of the Nuclear Regulatory Commission) tried valiently > to convey to the obstreperous reporter in the briefing, was that each country > develops its own regulations and that those might be based on different > presumed levels (odds) of safety or on different approaches in their analyses. > > Every metrologist must have an understanding of statistical analysis. They > deal with uncertainties in measurement, uncertainties in sampling, and the > propagation of uncertainties -- just to name a few cases. In fact, > measurements in lumens away from that one specified wavelength is a > statistical approximation in reality (but firm in the way it is defined). > > Epidemiologists also must understand statistical analysis. Those analyses are > used in drug safety trials, searches for causes of epidemics or diseases or > syndromes, analysis of the hazards of ionizing radiation, and so forth. > > I took a graduate level epidemiology course as part of the coursework for my > Master's in Environmental Studies. The prof came out to the front of the > class, introduced himself, and gave us our first and only indisputable > statistic: "Each and every one of you has a 100 % chance of dying." He then > went on to say that every thing said after that in the course would be an > approximation. > > People vary in their responses to health challenges. Also, in many cases > epidemiologists are working with extrapolations from higher levels of > challenge (e.g., radiation exposure) to lower levels. One might assume > straight-line, exponential, quadratic, cubic, or other sorts of methods to > use to extrapolate and usually the well-known data are insufficient to say > which is correct. And lastly, "small number statistics" are a field unto > their own and only marginally related to class grade curves and Gaussian > distributions. > > And so it is, folks. One cannot say that receiving more than 50 mSv is > absolutely harmful (100 % risk) and that receiving less than 50 mSv is > absolutely safe (0 % risk). Nothing in that region of exposure is well known. > > In the meantime, stay safe out there. > > Jim > > -- > James R. Frysinger > 632 Stony Point Mountain Road > Doyle, TN 38559-3030 > > (C) 931.212.0267 > (H) 931.657.3107 > (F) 931.657.3108 > >
