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  2. Algorithms for calculating variance - Wikipedia

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

    Therefore, a naïve algorithm to calculate the estimated variance is given by the following: Let n ← 0, Sum ← 0, SumSq ← 0. For each datum x: n ← n + 1. SumSum + x. SumSq ← SumSq + x × x. Var = (SumSq − (Sum × Sum) / n) / (n − 1) This algorithm can easily be adapted to compute the variance of a finite population: simply ...

  3. Summation - Wikipedia

    en.wikipedia.org/wiki/Summation

    t. e. In mathematics, summation is the addition of a sequence of numbers, called addends or summands; the result is their sum or total. Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.

  4. Variance - Wikipedia

    en.wikipedia.org/wiki/Variance

    The next expression states equivalently that the variance of the sum is the sum of the diagonal of covariance matrix plus two times the sum of its upper triangular elements (or its lower triangular elements); this emphasizes that the covariance matrix is symmetric. This formula is used in the theory of Cronbach's alpha in classical test theory.

  5. Sum of normally distributed random variables - Wikipedia

    en.wikipedia.org/wiki/Sum_of_normally...

    The characteristic function. of the sum of two independent random variables X and Y is just the product of the two separate characteristic functions: of X and Y. The characteristic function of the normal distribution with expected value μ and variance σ 2 is. {\displaystyle \varphi (t)=\exp \left (it\mu - {\sigma ^ {2}t^ {2} \over 2}\right).} So.

  6. Addition - Wikipedia

    en.wikipedia.org/wiki/Addition

    Addition (usually signified by the plus symbol +) is one of the four basic operations of arithmetic, the other three being subtraction, multiplication and division. [2] The addition of two whole numbers results in the total amount or sum of those values combined. The example in the adjacent image shows two columns of three apples and two apples ...

  7. Convolution of probability distributions - Wikipedia

    en.wikipedia.org/wiki/Convolution_of_probability...

    The probability distribution of the sum of two or more independent random variables is the convolution of their individual distributions. The term is motivated by the fact that the probability mass function or probability density function of a sum of independent random variables is the convolution of their corresponding probability mass functions or probability density functions respectively.

  8. How to calculate the present and future value of annuities - AOL

    www.aol.com/finance/calculate-present-future...

    Therefore, the future value of your regular $1,000 investments over five years at a 5 percent interest rate would be about $5,525.63. Note: This calculation assumes equal annual contributions and ...

  9. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    If one has a two-digit number, take it and add the two numbers together and put that sum in the middle, and one can get the answer. For example: 24 x 11 = 264 because 2 + 4 = 6 and the 6 is placed in between the 2 and the 4. Second example: 87 x 11 = 957 because 8 + 7 = 15 so the 5 goes in between the 8 and the 7 and the 1 is carried to the 8.