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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.
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An estimand is a quantity that is to be estimated in a statistical analysis. [1] The term is used to distinguish the target of inference from the method used to obtain an approximation of this target (i.e., the estimator) and the specific value obtained from a given method and dataset (i.e., the estimate). [2]
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.
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.
where s x 2 and s y 2 are the variances of the x and y variates respectively, m x and m y are the means of the x and y variates respectively and s xy is the covariance of x and y. Although the approximate variance estimator of the ratio given below is biased, if the sample size is large, the bias in this estimator is negligible.
Bias is a property of the estimator, not of the estimate. Often, people refer to a "biased estimate" or an "unbiased estimate", but they really are talking about an "estimate from a biased estimator", or an "estimate from an unbiased estimator". Also, people often confuse the "error" of a single estimate with the "bias" of an estimator.
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.