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  2. History of mathematical notation - Wikipedia

    en.wikipedia.org/wiki/History_of_mathematical...

    The history of mathematical notation [1] covers the introduction, development, and cultural diffusion of mathematical symbols and the conflicts between notational methods that arise during a notation's move to popularity or obsolescence. Mathematical notation [2] comprises the symbols used to write mathematical equations and formulas.

  3. 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.

  4. Notation in probability and statistics - Wikipedia

    en.wikipedia.org/wiki/Notation_in_probability...

    Random variables are usually written in upper case Roman letters, such as or and so on. Random variables, in this context, usually refer to something in words, such as "the height of a subject" for a continuous variable, or "the number of cars in the school car park" for a discrete variable, or "the colour of the next bicycle" for a categorical variable.

  5. σ-algebra - Wikipedia

    en.wikipedia.org/wiki/Σ-algebra

    In mathematical analysis and in probability theory, a σ-algebra ("sigma algebra"; also σ-field, where the σ comes from the German "Summe" [1]) on a set X is a nonempty collection Σ of subsets of X closed under complement, countable unions, and countable intersections. The ordered pair (,) is called a measurable space.

  6. Glossary of mathematical symbols - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_mathematical...

    3. Between two groups, may mean that the first one is a proper subgroup of the second one. > (greater-than sign) 1. Strict inequality between two numbers; means and is read as "greater than". 2. Commonly used for denoting any strict order. 3. Between two groups, may mean that the second one is a proper subgroup of the first one. ≤ 1.

  7. Mathematical notation - Wikipedia

    en.wikipedia.org/wiki/Mathematical_notation

    It is believed that a notation to represent numbers was first developed at least 50,000 years ago. [3] Early mathematical ideas such as finger counting [ 4 ] have also been represented by collections of rocks, sticks, bone, clay, stone, wood carvings, and knotted ropes.

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

    www.aol.com/news/teens-mean-sigma-210752971.html

    Urban Dictionary adds that sigma “is what all 10 year olds think they are.” As reported by British GQ, the word “sigma” was born from the misogynistic “manosphere. ...

  9. Standard deviation - Wikipedia

    en.wikipedia.org/wiki/Standard_deviation

    For example, assume an investor had to choose between two stocks. Stock A over the past 20 years had an average return of 10 percent, with a standard deviation of 20 percentage points (pp) and Stock B, over the same period, had average returns of 12 percent but a higher standard deviation of 30 pp. On the basis of risk and return, an investor ...