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 weighted harmonic mean of precision and recall with weights formula_20. Their relationship is formula_21 where formula_22. There are other parameters and strategies for performance metric of information retrieval system, such as the area under the ROC curve (AUC). For web document retrieval, if the user's objectives are not clear, the precision and recall can't be optimized. As summarized by Lopresti, Precision and recall In pattern recognition, information retrieval and binary classification, precision (also called positive predictive value) is the fraction of relevant instances among the retrieved instances, while recall (also known as sensitivity) is the fraction of relevant instances that