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  2. Return period - Wikipedia

    en.wikipedia.org/wiki/Return_period

    The theoretical return period between occurrences is the inverse of the average frequency of occurrence. For example, a 10-year flood has a 1/10 = 0.1 or 10% chance of being exceeded in any one year and a 50-year flood has a 0.02 or 2% chance of being exceeded in any one year.

  3. Significant figures - Wikipedia

    en.wikipedia.org/wiki/Significant_figures

    An exact number has an infinite number of significant figures. If the number of apples in a bag is 4 (exact number), then this number is 4.0000... (with infinite trailing zeros to the right of the decimal point). As a result, 4 does not impact the number of significant figures or digits in the result of calculations with it.

  4. 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.

  5. Equity premium puzzle - Wikipedia

    en.wikipedia.org/wiki/Equity_premium_puzzle

    The process of calculating the equity risk premium, and selection of the data used, is highly subjective to the study in question, but is generally accepted to be in the range of 3–7% in the long-run. Dimson et al. calculated a premium of "around 3–3.5% on a geometric mean basis" for global equity markets during 1900–2005 (2006). [7]

  6. Standard deviation - Wikipedia

    en.wikipedia.org/wiki/Standard_deviation

    The reciprocals of the square roots of these two numbers give us the factors 0.45 and 31.9 given above. A larger population of N = 10 has 9 degrees of freedom for estimating the standard deviation. The same computations as above give us in this case a 95% CI running from 0.69 × SD to 1.83 × SD.

  7. Tsiolkovsky rocket equation - Wikipedia

    en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

    A rocket's required mass ratio as a function of effective exhaust velocity ratio. The classical rocket equation, or ideal rocket equation is a mathematical equation that describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity and can thereby move due to the ...

  8. Elo rating system - Wikipedia

    en.wikipedia.org/wiki/Elo_rating_system

    Arpad Elo was a chess master and an active participant in the United States Chess Federation (USCF) from its founding in 1939. [4] The USCF used a numerical ratings system devised by Kenneth Harkness to enable members to track their individual progress in terms other than tournament wins and losses.

  9. Real wages - Wikipedia

    en.wikipedia.org/wiki/Real_wages

    For example, the average worker’s paycheck increased 2.7% in 2005, while it increased 2.1% in 2015, creating an impression for some workers that they were "falling behind". [3] However, inflation was 3.4% in 2005, while it was only 0.1% in 2015, so workers were actually "getting ahead" with lower nominal paycheck increases in 2015 compared to ...