Guesstimate is an informal English portmanteau of guess and estimate, first used by American statisticians in 1934 or 1935. It is defined as an estimate made without using adequate or complete information, or, more strongly, as an estimate arrived at by guesswork or conjecture. Like the words estimate and guess, guesstimate may be used as a verb or a noun (with the same change in pronunciation as estimate). A guesstimate may be a first rough approximation pending a more accurate estimate, or it may be an educated guess at something for which no better information will become available.
Guesstimation techniques are used:
- in physics, where the use of guesstimation techniques to solve Fermi problems is taught as a useful skill to science students.
- in cosmology, where the Drake equation is a well-known guesstimation method.
- in economics, where economic forecasts and statistics are often based on guesstimates.
Lawrence Weinstein and John Adam's book Guesstimation: Solving the World's Problems on the Back of a Cocktail Napkin, based on the course "Physics on the Back of an Envelope" at Old Dominion University, promotes guesstimation techniques as a useful life skill. It includes many worked examples of guesstimation, including the following problems:
- How many total miles do all Americans drive in a year?
- Answer: about two trillion (2x1012).
- How much high-level nuclear waste does a 1 GW nuclear power plant produce in a year?
- Answer: about sixty tons.
See also 
|Look up guesstimate in Wiktionary, the free dictionary.|
- guess Online Etymological Dictionary
- guesstimate Dictionary.com Unabridged (v 1.1)
- guesstimate Merriam-Webster On-line Dictionary
- guesstimate MSN Encarta Dictionary. Archived 2009-10-31.
- guesstimate American Heritage Dictionary
- Compact Oxford English Dictionary guesstimate
- "Guesstimate with confidence using confidence intervals" from back cover of Statistics for Dummies
- Guesstimate; Grades 4-6 NTTI Lesson Plan
- Guesstimation: Solving the World's Problems on the Back of a Cocktail Napkin, Tony Mann, Times Higher Education Supplement
- The Drake Equation WeAreNotAlone.net
- Economic outlooks often rely on guesstimation, M. Ray Perryman, San Antonio Business Journal
- Weinstein & Adam (2008) Problem 5.1
- Weinstein & Adam (2008) Problem 10.5