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  2. Algorithms for calculating variance - Wikipedia

    en.wikipedia.org/wiki/Algorithms_for_calculating...

    This algorithm can easily be adapted to compute the variance of a finite population: simply divide by n instead of n − 1 on the last line.. Because SumSq and (Sum×Sum)/n can be very similar numbers, cancellation can lead to the precision of the result to be much less than the inherent precision of the floating-point arithmetic used to perform the computation.

  3. Log-normal distribution - Wikipedia

    en.wikipedia.org/wiki/Log-normal_distribution

    Comparison of mean, median and mode of two log-normal distributions with different skewness. The mode is the point of global maximum of the probability density function. In particular, by solving the equation (⁡) ′ =, we get that: ⁡ [] =.

  4. Variance - Wikipedia

    en.wikipedia.org/wiki/Variance

    Firstly, if the true population mean is unknown, then the sample variance (which uses the sample mean in place of the true mean) is a biased estimator: it underestimates the variance by a factor of (n − 1) / n; correcting this factor, resulting in the sum of squared deviations about the sample mean divided by n-1 instead of n, is called ...

  5. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    It is also the continuous distribution with the maximum entropy for a specified mean and variance. [18] [19] Geary has shown, assuming that the mean and variance are finite, that the normal distribution is the only distribution where the mean and variance calculated from a set of independent draws are independent of each other. [20] [21]

  6. Expected value - Wikipedia

    en.wikipedia.org/wiki/Expected_value

    Expected values can also be used to compute the variance, by means of the computational formula for the variance ⁡ = ⁡ [] (⁡ []). A very important application of the expectation value is in the field of quantum mechanics.

  7. Bachelier model - Wikipedia

    en.wikipedia.org/wiki/Bachelier_model

    The European analytic formula for this model based on a risk neutral argument is derived in Analytic Formula for the European Normal Black Scholes Formula (Kazuhiro Iwasawa, New York University, December 2, 2001). [3] The implied volatility under the Bachelier model can be obtained by an accurate numerical approximation. [4]

  8. Weibull distribution - Wikipedia

    en.wikipedia.org/wiki/Weibull_distribution

    In probability theory and statistics, the Weibull distribution / ˈ w aɪ b ʊ l / is a continuous probability distribution.It models a broad range of random variables, largely in the nature of a time to failure or time between events.

  9. Pooled variance - Wikipedia

    en.wikipedia.org/wiki/Pooled_variance

    In statistics, pooled variance (also known as combined variance, composite variance, or overall variance, and written ) is a method for estimating variance of several different populations when the mean of each population may be different, but one may assume that the variance of each population is the same. The numerical estimate resulting from ...