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The UN defines water supplies as ‘improved’ or ‘unimproved.’ These indicators are easy to measure, but do not reflect water quality, which requires laboratory or field tests. Laboratory and test availability, expense and technical capacity are obstacles for developing countries. This research compares and verifies four low-cost, field-based microbiological tests: the EC-Kit (Colilert® and Petrifilm™ tests), the H2S bacteria test, and Easygel®, against a standard method (Quanti-Tray®). The objectives are to: (1) verify the accuracy of the four field-based tests, (2) study the accuracy of these tests as a function of improved and unimproved sources; (3) recommend a single microbiological test, if appropriate, based on accuracy and cost, and/or (4) recommend a testing combination, if appropriate, based on accuracy and cost. The tests of 500+ total water samples from Capiz Province, Philippines and Cambridge, MA indicate that two-tests systems gave better results than a single test. Both the 100-mL H2S test + Petrifilm™ and the 20-mL H2S test + Easygel® combinations yield promising results, in addition to being inexpensive. None of the field-based tests should be used on their own. We recommend further verification of a larger sample size and scale be undertaken before these testing combinations are recommended for wider use.

a b s t r a c tA conventional wisdom about the progress of physics holds that successive theories wholly encompass the domains of their predecessors through a process that is often called "reduction." While certain influential accounts of inter-theory reduction in physics take reduction to require a single "global" derivation of one theory's laws from those of another, I show that global reductions are not available in all cases where the conventional wisdom requires reduction to hold. However, I argue that a weaker "local" form of reduction, which defines reduction between theories in terms of a more fundamental notion of reduction between models of a single fixed system, is available in such cases and moreover suffices to uphold the conventional wisdom. To illustrate the sort of fixed-system, inter-model reduction that grounds inter-theoretic reduction on this picture, I specialize to a particular class of cases in which both models are dynamical systems. I show that reduction in these cases is underwritten by a mathematical relationship that follows a certain liberalized construal of Nagel/Schaffner reduction, and support this claim with several examples. Moreover, I show that this broadly Nagelian analysis of inter-model reduction encompasses several cases that are sometimes cited as instances of the "physicist's" limit-based notion of reduction.

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