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  2. 68–95–99.7 rule - Wikipedia

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

    In the social sciences, a result may be considered statistically significant if its confidence level is of the order of a two-sigma effect (95%), while in particle physics and astrophysics, there is a convention of requiring statistical significance of a five-sigma effect (99.99994% confidence) to qualify as a discovery.

  3. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    About 68% of values drawn from a normal distribution are within one standard deviation σ from the mean; about 95% of the values lie within two standard deviations; and about 99.7% are within three standard deviations. [8] This fact is known as the 68–95–99.7 (empirical) rule, or the 3-sigma rule.

  4. Sigma bond - Wikipedia

    en.wikipedia.org/wiki/Sigma_bond

    A molecule with no rings can be represented as a tree with a number of bonds equal to the number of atoms minus one (as in dihydrogen, H 2, with only one sigma bond, or ammonia, NH 3, with 3 sigma bonds). 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 ...

  5. Methyl group - Wikipedia

    en.wikipedia.org/wiki/Methyl_group

    In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula CH 3 (whereas normal methane has the formula CH 4). In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many organic compounds. It is a very stable group in ...

  6. Standard deviation - Wikipedia

    en.wikipedia.org/wiki/Standard_deviation

    A five-sigma level translates to one chance in 3.5 million that a random fluctuation would yield the result. This level of certainty was required in order to assert that a particle consistent with the Higgs boson had been discovered in two independent experiments at CERN , [ 11 ] also leading to the declaration of the first observation of ...

  7. IUPAC numerical multiplier - Wikipedia

    en.wikipedia.org/wiki/IUPAC_numerical_multiplier

    1 mono- 30 triaconta- 2 di- 31 hentriaconta- 3 tri- 32 dotriaconta- 4 tetra- 33 tritriaconta- 5 penta- 34 tetratriaconta- 6 hexa- 40 tetraconta- 7 hepta- 50

  8. Arithmetical hierarchy - Wikipedia

    en.wikipedia.org/wiki/Arithmetical_hierarchy

    Because every first-order formula has a prenex normal form, every formula is assigned at least one classification. Because redundant quantifiers can be added to any formula, once a formula is assigned the classification Σ n 0 {\displaystyle \Sigma _{n}^{0}} or Π n 0 {\displaystyle \Pi _{n}^{0}} it will be assigned the classifications Σ m 0 ...

  9. Alkyl group - Wikipedia

    en.wikipedia.org/wiki/Alkyl_group

    In organic chemistry, an alkyl group is an alkane missing one hydrogen. [1] The term alkyl is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of −C n H 2n+1. A cycloalkyl group is derived from a cycloalkane by removal of a hydrogen atom from a ring and has the general formula −C n H ...