In some texts, the interquartile range is defined differently. It is defined as the difference between the largest and smallest values in the middle 50% of a set of data. To compute an interquartile range using this definition, first remove observations from the lower quartile.
A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal.
The first electronic device ever invented is the relay, a remote switch controlled by electricity that was invented in 1835 by Joseph Henry, an American scientist, although it is also claimed that the English inventor Edward Davy certainly invented the electric relay in his electric telegraph c.1835.