Rules For Detecting Signals
The most common sets are:
- The Western Electric rules
- The Wheeler rules (equivalent to the Western Electric zone tests)
- The Nelson rules
There has been particular controversy as to how long a run of observations, all on the same side of the centre line, should count as a signal, with 6, 7, 8 and 9 all being advocated by various writers.
The most important principle for choosing a set of rules is that the choice be made before the data is inspected. Choosing rules once the data have been seen tends to increase the Type I error rate owing to testing effects suggested by the data.
Read more about this topic: Control Chart
Famous quotes containing the words rules for, rules, detecting and/or signals:
“The young break rules for fun. The old for profit.”
—Mason Cooley (b. 1927)
“Life is a game in which the rules are constantly changing; nothing spoils a game more than those who take it seriously. Adultery? Phooey! You should never subjugate yourself to another nor seek the subjugation of someone else to yourself. If you follow that Crispian principle you will be able to say “Phooey,” too, instead of reaching for your gun when you fancy yourself betrayed.”
—Quentin Crisp (b. 1908)
“In our Mechanics’ Fair, there must be not only bridges, ploughs, carpenter’s planes, and baking troughs, but also some few finer instruments,—rain-gauges, thermometers, and telescopes; and in society, besides farmers, sailors, and weavers, there must be a few persons of purer fire kept specially as gauges and meters of character; persons of a fine, detecting instinct, who note the smallest accumulations of wit and feeling in the bystander.”
—Ralph Waldo Emerson (1803–1882)
“The term preschooler signals another change in our expectations of children. While toddler refers to physical development, preschooler refers to a social and intellectual activity: going to school. That shift in emphasis is tremendously important, for it is at this age that we think of children as social creatures who can begin to solve problems.”
—Lawrence Kutner (20th century)