Science and engineering in Manchester chemist visited Manchester in the 1840s. In his research in Manchester, Smith discovered the existence of acid rain, a by product of the industrial revolution. Smith consequently pushed for greater environmental awareness and helped to found the Noxious Vapours Abatement Society in Manchester, which raised awareness of the consequences of poor air. Joseph Whitworth was an engineer and inventor who hailed from Stockport, Cheshire (now Greater Manchester). A talented mechanic amongst various other engineering roles, for long periods of his life, he worked in factories in Manchester. Whitworth would ultimately devise a standard screw thread system, the first of its
Precision and recall formula_10 measure, because recall and precision are evenly weighted. It is a special case of the general formula_11 measure (for non-negative real values of formula_12): formula_13 Two other commonly used formula_14 measures are the formula_15 measure, which weights recall higher than precision, and the formula_16 measure, which puts more emphasis on precision than recall. The F-measure was derived by van Rijsbergen (1979) so that formula_11 "measures the effectiveness of retrieval with respect to a user who attaches formula_12 times as much importance to recall as precision". It is based on van Rijsbergen's effectiveness measure formula_19, the second term being the