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  2. Uncertainty - Wikipedia

    en.wikipedia.org/wiki/Uncertainty

    In that case, the quoted standard errors are easily converted to 68.3% ("one sigma"), 95.4% ("two sigma"), or 99.7% ("three sigma") confidence intervals. [citation needed] In this context, uncertainty depends on both the accuracy and precision of the measurement instrument. The lower the accuracy and precision of an instrument, the larger the ...

  3. Standard error - Wikipedia

    en.wikipedia.org/wiki/Standard_error

    In many practical applications, the true value of σ is unknown. As a result, we need to use a distribution that takes into account that spread of possible σ's. When the true underlying distribution is known to be Gaussian, although with unknown σ, then the resulting estimated distribution follows the Student t-distribution.

  4. Uncertainty quantification - Wikipedia

    en.wikipedia.org/wiki/Uncertainty_quantification

    In this case, even if there is no unknown parameter in the model, a discrepancy is still expected between the model and true physics. Algorithmic Also known as numerical uncertainty, or discrete uncertainty. This type comes from numerical errors and numerical approximations per implementation of the computer model.

  5. 68–95–99.7 rule - Wikipedia

    en.wikipedia.org/wiki/68–95–99.7_rule

    In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

  6. Kalman filter - Wikipedia

    en.wikipedia.org/wiki/Kalman_filter

    The unscented Kalman filter (UKF) [67] uses a deterministic sampling technique known as the unscented transformation (UT) to pick a minimal set of sample points (called sigma points) around the mean. The sigma points are then propagated through the nonlinear functions, from which a new mean and covariance estimate are then formed.

  7. What do teens mean when they say ‘sigma’? - AOL

    www.aol.com/news/teens-mean-sigma-000158935.html

    Sigma males are “considered ‘equal’ to Alphas on the hierarchy but live outside of the hierarchy by choice,” reads the website. Urban Dictionary adds that sigma “is what all 10 year olds ...

  8. Sigma - Wikipedia

    en.wikipedia.org/wiki/Sigma

    Today, it is known as lunate sigma (uppercase Ϲ, lowercase ϲ), because of its crescent-like shape, and is still widely used in decorative typefaces in Greece, especially in religious and church contexts, as well as in some modern print editions of classical Greek texts.

  9. Sample size determination - Wikipedia

    en.wikipedia.org/wiki/Sample_size_determination

    Let X i, i = 1, 2, ..., n be independent observations taken from a normal distribution with unknown mean μ and known variance σ 2. Consider two hypotheses, a null hypothesis: : = and an alternative hypothesis: : = for some 'smallest significant difference' μ * > 0. This is the smallest value for which we care about observing a difference.