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
Accuracy and precision More sophisticated metrics, such as discounted cumulative gain, take into account each individual ranking, and are more commonly used where this is important. Accuracy and precision Precision is a description of "random errors", a measure of statistical variability. Accuracy has two definitions: In simplest terms, given a set of data points from repeated measurements of the same quantity, the set can be said to be "precise" if the values are close to each other, while the set can be said to be "accurate" if their average is close to the "true value" of the quantity being measured. In the first,