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A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. Compare this to heuristic, a similar concept used in mathematical discourse, or in computer science, particularly in algorithm design. See also mnemonic. Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... Look up Heuristic in Wiktionary, the free dictionary. ... Euclid, Greek mathematician, 3rd century BC, as imagined by by Raphael in this detail from The School of Athens. ... Computer scaence, or computing science, is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. ... In mathematics, computing, linguistics, and related disciplines, an algorithm is a finite list of well-defined instructions for accomplishing some task that, given an initial state, will terminate in a defined end-state. ... Wikiquote has a collection of quotations related to: English mnemonics A mnemonic (pronounced in RP, [nɪmɑnɪk] in GA) is a memory aid, and most serve an educational purpose. ...

Origin of the term

The term "rule of thumb" (or a similar phrase) stands in many languages and cultures for "quickly understood, easily used, practical method yielding approximate results".

Use as a physical measurement

The measurement of an inch is derived from the distance between the base of the thumbnail and the first joint. This is a plausible origin as the thumb is often used for rough measurement by carpenters, seamstresses, artists and many others. This connection to anatomy is also present in other languages. For example, the French phrase un pouce means both "a thumb" and "an inch", and the Portuguese word for "inch" is polegada, which means "a thumb's length" (from polegar, meaning thumb). An inch (plural: inches; symbol or abbreviation: in or, sometimes, ″ - a double prime) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ...

Distance approximation

The distance of a far-away object can be estimated by comparing the height of ones thumb at an arms distance to the perceptive height of a distant tree or building which height could be readily estimated. This method would be generally imprecise and the result would mainly be based on the experience of the person making the estimation.

Hours of Daylight Remaining

Hold your outstretched hand horizontal at arm's length with your palm facing you; for each hand width the sun is above the horizon, there is one remaining hour of sunlight.

Used to determine wind direction

A technique for approximating the general direction of the wind involves wetting the thumb then raising it in the air.

Used to measure the coldness of beer

In England, before the advent of thermometers, bar-tenders used to stick their thumbs in a beer to ensure its coldness. It is also said that it was standard practice at this time to stick one's thumb into the boiled wort to ensure that it wasn't too hot to accommodate the yeast.

Domestic violence/discipline

It is often claimed that the term originally referred to the maximum thickness of a stick with which it was permissible for a man to beat his wife.^[1] This explanation for the origin of the term was popularized in the opening of the 1999 movie The Boondock Saints. This article or section does not cite any references or sources. ... Year 1999 (MCMXCIX) was a common year starting on Friday (link will display full 1999 Gregorian calendar). ... The Boondock Saints is a 1999 action crime drama film written and directed by Troy Duffy. ...

Caricature condemning Buller: Judge Thumb - Patent Sticks for Family Correction - Warranted Lawful!

Linguist Michael Quinion, citing the research of Sharon Fenick, notes that there are some examples of a related usage historically — most notably with regard to a supposed pronouncement by a British judge, Sir Francis Buller, that a man may legally beat his wife, provided that he used a stick no thicker than his thumb. However, it is questionable whether Buller ever made such a pronouncement and there is even less evidence that he phrased it as a "rule of thumb"; the rumoured statement was so unpopular that it caused him to be lambasted as "Judge Thumb" in a satirical James Gillray cartoon. According to Quinion, the term "Rule of Thumb" was first documented in English in 1692, long before Buller's reported pronouncement. The first known usage of the phrase "rule of thumb" in direct reference to domestic violence was in 1976, in the book Battered Wives by Del Martin. Image File history File links Download high resolution version (688x960, 107 KB) Caption: Judge Thumb says: Who wants a cure for a nasty Wife? Heres your nice Family Amusement for Winter Evenings! Who buys here? Woman says: Help! Murder, for God sake, Murder! Man says: Murder, hey? is Law... Image File history File links Download high resolution version (688x960, 107 KB) Caption: Judge Thumb says: Who wants a cure for a nasty Wife? Heres your nice Family Amusement for Winter Evenings! Who buys here? Woman says: Help! Murder, for God sake, Murder! Man says: Murder, hey? is Law... Michael Quinion in his office Michael Quinion is the author and creator the the site World Wide Words. ... James Gillray James Gillray, sometimes spelled Gilray (born August 13, 1757 in Chelsea; died June 1, 1815), was a British caricaturist and printmaker famous for his etched political and social satires, mainly published between 1792 and 1810. ... Events February 13 - Massacre of Glencoe March 1 - The Salem witch trials begin in Salem Village, Massachusetts Bay Colony with the charging of three women with witchcraft. ... Year 1976 (MCMLXXVI) was a leap year starting on Thursday (link will display full calendar) of the 1976 Gregorian calendar. ... Del Martin (born May 5, 1921) and Phyllis Lyon (born 1924) are an American lesbian couple known as feminist and gay-rights activists. ...

Used for plate settings at the Royal table

A technique for setting a row of plates an equal distance from the table edge. Plate setters, setting plates for an English Royal banquet, place the plate against the tip of the thumb while holding the arch of the thumb and first finger against the table edge.

The Russian Tsar

The Russian Tsar Nicholas I has been suggested as the creator of this term. In an apocryphal story he is said to have drawn the route of a railroad from St. Petersburg to Moscow, accidentally tracing his thumb. The engineers, nervous about disobeying his orders, laid the tracks with an unnecessary curve according to the line drawn. Nicholas I (Russian: Николай I Павлович, Nikolai I Pavlovich), July 6 (June 25, Old Style), 1796–March 2 (18 February Old Style), 1855), was the Emperor of Russia from 1825 until 1855, known as one of the most reactionary of the Russian monarchs. ...

Examples of usage

Financial - Rule of 72 A rule of thumb for exponential growth at a constant rate. An approximation of the "doubling time" formula used in population growth, which says divide 70 by the percent growth rate (the actual number is 69.3147181 from the natural logarithm of 2). In terms of money, it is frequently easier to use 72 (rather than 70) because it is easily divisible by many more factors than 70 (or 69.3). Therefore, divide 72 by the percent interest rate to determine the approximate amount of time to double your money in an investment. For example, at 8% interest, your money will double in approximately 9 years (72/8 = 9). In finance, the rule of 72, the rule of 70 and the rule of 69. ... In mathematics, exponential growth (or geometric growth) occurs when the growth rate of a function is always proportional to the functions current size. ...

Tailors' Rule of Thumb A simple approximation that was used by tailors to determine the wrist, neck, and waist circumferences of a person through one single measurement of the circumference of that person's thumb. The rule states, typically, that twice the circumference of a person's thumb is the circumference of their wrist, twice the circumference of the wrist is the circumference of the neck, and twice around the neck is the person's waist. For example, if the circumference of the thumb is 4 inches, then the wrist circumference is 8 inches, the neck is 16 and the waist is 32. An interesting consequence of this is that — for those to whom the rule applies — this simple method can be used to determine if trousers will fit: the trousers are wrapped around the neck, and if the two ends barely touch, then they will fit. Any overlap or lack thereof corresponds to the trousers being too loose or tight, respectively. It has been suggested that this article or section be merged with estimation. ... In human anatomy, the wrist is the flexible and narrower connection between the forearm and the hand. ... A human neck. ... Waistline The waist is the part of the abdomen between the ribcage and hips. ... The circumference is the distance around a closed curve. ...

Marine Navigation A ship's captain should navigate to keep the ship more than a thumb's width from the shore, as shown on the nautical chart being used. Thus, with a coarse scale chart, that provides few details of nearshore hazards such as rocks, a thumb's width would represent a great distance, and the ship would be steered far from shore; whereas on a fine scale chart, in which more detail is provided, a ship could be brought closer to shore.^[2]

Statistics The Statistical Rule of Thumb says that for most large data sets, 68% of data points will occur within one standard deviation from the mean, and 95% will occur within two standard deviations. Chebyshev's inequality is a more general rule along these same lines and applies to all data sets. In probability and statistics, the standard deviation of a probability distribution, random variable, or population or multiset of values is a measure of the spread of its values. ... In probability theory, Chebyshevs inequality (also known as Tchebysheffs inequality, Chebyshevs theorem, or the Bienaymé-Chebyshev inequality), named after Pafnuty Chebyshev, who first proved it, states that in any data sample or probability distribution, nearly all the values are close to the mean value, and provides a...

References

External links

• A collection of various Rules of Thumb - A wiki based collection of user submitted rules of thumb

See also

• Heuristic argument
• Common sense