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Guesstimate is an informal English portmanteau of guess and estimate, first used by American statisticians in 1934 [1] or 1935. [2] It is defined as an estimate made without using adequate or complete information, [3] [4] or, more strongly, as an estimate arrived at by guesswork or conjecture. [2] [5] [6] Like the words estimate and guess ...
Twinkl was founded by husband and wife Jonathan and Susie Seaton. [2] [3] Susie, a primary school teacher, had noticed there was a lack of ready-made, high-quality educational materials and classroom content available to teachers.
An estimate that turns out to be incorrect will be an overestimate if the estimate exceeds the actual result [3] and an underestimate if the estimate falls short of the actual result. [ 4 ] The confidence in an estimate is quantified as a confidence interval , the likelihood that the estimate is in a certain range.
For a value that is sampled with an unbiased normally distributed error, the above depicts the proportion of samples that would fall between 0, 1, 2, and 3 standard deviations above and below the actual value.
[2] [3] Estimation statistics is sometimes referred to as the new statistics. [3] [4] [5] The primary aim of estimation methods is to report an effect size (a point estimate) along with its confidence interval, the latter of which is related to the precision of the estimate. [6]
These values are used to calculate an E value for the estimate and a standard deviation (SD) as L-estimators, where: E = (a + 4m + b) / 6 SD = (b − a) / 6. E is a weighted average which takes into account both the most optimistic and most pessimistic estimates provided. SD measures the variability or uncertainty in the estimate.
Thus one will expect to be within 1 ⁄ 8 to 8 times the correct value – within an order of magnitude, and much less than the worst case of erring by a factor of 2 9 = 512 (about 2.71 orders of magnitude). If one has a shorter chain or estimates more accurately, the overall estimate will be correspondingly better.
The defining characteristic of back-of-the-envelope calculations is the use of simplified assumptions. A similar phrase in the U.S. is "back of a napkin", also used in the business world to describe sketching out a quick, rough idea of a business or product. [1] In British English, a similar idiom is "back of a fag packet".