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  2. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    The standard deviation of the distribution is (sigma). A random variable with a Gaussian distribution is said to be normally distributed , and is called a normal deviate . Normal distributions are important in statistics and are often used in the natural and social sciences to represent real-valued random variables whose distributions are not ...

  3. 68–95–99.7 rule - Wikipedia

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

    Diagram showing the cumulative distribution function for the normal distribution with mean (μ) 0 and variance (σ 2) 1. These numerical values "68%, 95%, 99.7%" come from the cumulative distribution function of the normal distribution. The prediction interval for any standard score z corresponds numerically to (1 − (1 − Φ μ,σ 2 (z)) · 2).

  4. Non-linear sigma model - Wikipedia

    en.wikipedia.org/wiki/Non-linear_sigma_model

    In quantum field theory, a nonlinear σ model describes a field Σ which takes on values in a nonlinear manifold called the target manifold T.The non-linear σ-model was introduced by Gell-Mann & Lévy (1960, section 6), who named it after a field corresponding to a spinless meson called σ in their model. [1]

  5. Standard deviation - Wikipedia

    en.wikipedia.org/wiki/Standard_deviation

    For example, if the product needs to be opened and drained and weighed, or if the product was otherwise used up by the test. In experimental science, a theoretical model of reality is used. Particle physics conventionally uses a standard of "5 sigma" for the declaration of a discovery. A five-sigma level translates to one chance in 3.5 million ...

  6. Sigmoid function - Wikipedia

    en.wikipedia.org/wiki/Sigmoid_function

    Examples of the application of the logistic S-curve to the response of crop yield (wheat) to both the soil salinity and depth to water table in the soil are shown in modeling crop response in agriculture. In artificial neural networks, sometimes non-smooth functions are used instead for efficiency; these are known as hard sigmoids.

  7. Log-normal distribution - Wikipedia

    en.wikipedia.org/wiki/Log-normal_distribution

    For example, the log-normal function with such fits well with the size of secondarily produced droplets during droplet impact [56] and the spreading of an epidemic disease. [ 57 ] The value σ = 1 / 6 {\textstyle \sigma =1{\big /}{\sqrt {6}}} is used to provide a probabilistic solution for the Drake equation.

  8. Gaussian function - Wikipedia

    en.wikipedia.org/wiki/Gaussian_function

    Some examples include: In statistics and probability theory , Gaussian functions appear as the density function of the normal distribution , which is a limiting probability distribution of complicated sums, according to the central limit theorem .

  9. Sigma model - Wikipedia

    en.wikipedia.org/wiki/Sigma_model

    The model may or may not be quantized. An example of the non-quantized version is the Skyrme model; it cannot be quantized due to non-linearities of power greater than 4. In general, sigma models admit (classical) topological soliton solutions, for example, the skyrmion for the Skyrme model.