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毕业设计

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针阀体座面跳动量具的设计,毕业设计

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In the fields ofscience,engineering,industryandstatistics, theaccuracy1of ameasurementsystem is the degree of closeness of measurements of aquantityto that quantitys actual (true)value. Theprecision1of a measurement system, also calledreproducibilityorrepeatability, is the degree to which repeated measurements under unchanged conditions show the sameresults.2Although the two wordsreproducibilityandrepeatabilitycan besynonymousincolloquialuse, they are deliberately contrasted in the context of thescientific method.Accuracy indicates proximity of measurement results to the true value, precision to the repeatability or reproducibility of the measurementA measurement system can be accurate but not precise, precise but not accurate, neither, or both. For example, if anexperimentcontains asystematic error, then increasing thesample sizegenerally increases precision but does not improve accuracy. The result would be a consistent yet inaccurate string of results from the flawed experiment. Eliminating the systematic error improves accuracy but does not change precision.A measurement system is designatedvalidif it is bothaccurateandprecise. Related terms includebias(non-randomor directed effects caused by a factor or factors unrelated to theindependent variable) anderror(random variability).The terminology is also applied to indirect measurementsthat is, values obtained by a computational procedure from observed data.In addition to accuracy and precision, measurements may also have ameasurement resolution, which is the smallest change in the underlying physical quantity that produces a response in the measurement.In the case of full reproducibility, such as when rounding a number to a representablefloating pointnumber, the wordprecisionhas a meaning not related to reproducibility. For example, in theIEEE 754-2008standard it means the number of bits in thesignificand, so i