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  2. 68–95–99.7 rule - Wikipedia

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

    In the empirical sciences, the so-called three-sigma rule of thumb (or 3 σ rule) expresses a conventional heuristic that nearly all values are taken to lie within three standard deviations of the mean, and thus it is empirically useful to treat 99.7% probability as near certainty.

  3. Sigma bond - Wikipedia

    en.wikipedia.org/wiki/Sigma_bond

    There is no more than 1 sigma bond between any two atoms. Molecules with rings have additional sigma bonds, such as benzene rings, which have 6 C−C sigma bonds within the ring for 6 carbon atoms. The anthracene molecule, C 14 H 10, has three rings so that the rule gives the number of sigma bonds as 24 + 3 − 1 = 26. In this case there are 16 ...

  4. 3-sigma - Wikipedia

    en.wikipedia.org/?title=3-sigma&redirect=no

    This page was last edited on 24 September 2024, at 05:21 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.

  5. 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 ...

  6. Triple bond - Wikipedia

    en.wikipedia.org/wiki/Triple_bond

    When the atoms approach each other, the sp orbitals overlap to form an sp-sp sigma bond. At the same time the p z-orbitals approach and together they form a p z-p z pi-bond. Likewise, the other pair of p y-orbitals form a p y-p y pi-bond. The result is formation of one sigma bond and two pi bonds.

  7. Sigmatropic reaction - Wikipedia

    en.wikipedia.org/wiki/Sigmatropic_reaction

    An odd number is an indication of the involvement of a charged C atom or of a heteroatom lone pair replacing a CC double bond. Thus, [1,5] and [3,3] shifts become [1,4] and [2,3] shifts with heteroatoms, while preserving symmetry considerations. Hydrogens are omitted in the third example for clarity.

  8. Hyundai Sigma engine - Wikipedia

    en.wikipedia.org/wiki/Hyundai_Sigma_engine

    The Hyundai Sigma engine is what Hyundai Motor Company called the Mitsubishi 6G7 engine when ... (both also called the 3.5 D ) are the large 3,497 cc (3.5 L; 213.4 cu ...

  9. Control chart - Wikipedia

    en.wikipedia.org/wiki/Control_chart

    Even when a process is in control (that is, no special causes are present in the system), there is approximately a 0.27% probability of a point exceeding 3-sigma control limits. So, even an in control process plotted on a properly constructed control chart will eventually signal the possible presence of a special cause, even though one may not ...