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  2. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    If ⁠ ⁠ is a standard normal deviate, then = + will have a normal distribution with expected value ⁠ ⁠ and standard deviation ⁠ ⁠. This is equivalent to saying that the standard normal distribution ⁠ Z {\displaystyle Z} ⁠ can be scaled/stretched by a factor of ⁠ σ {\displaystyle \sigma } ⁠ and shifted by ⁠ μ ...

  3. Sum of normally distributed random variables - Wikipedia

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

    This is the characteristic function of the normal distribution with expected value + and variance + Finally, recall that no two distinct distributions can both have the same characteristic function, so the distribution of X + Y must be just this normal distribution.

  4. Expected value - Wikipedia

    en.wikipedia.org/wiki/Expected_value

    The mass of probability distribution is balanced at the expected value, here a Beta(α,β) distribution with expected value α/(α+β). In classical mechanics , the center of mass is an analogous concept to expectation.

  5. Log-normal distribution - Wikipedia

    en.wikipedia.org/wiki/Log-normal_distribution

    In hydrology, the log-normal distribution is used to analyze extreme values of such variables as monthly and annual maximum values of daily rainfall and river discharge volumes. [ 78 ] The image on the right, made with CumFreq , illustrates an example of fitting the log-normal distribution to ranked annually maximum one-day rainfalls showing ...

  6. 68–95–99.7 rule - Wikipedia

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

    In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr or 3 σ, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean ...

  7. Truncated normal distribution - Wikipedia

    en.wikipedia.org/wiki/Truncated_normal_distribution

    3 Generating values from the truncated normal distribution. 4 See also. ... the truncated normal distribution is the probability distribution derived from that of a ...

  8. Chi-squared distribution - Wikipedia

    en.wikipedia.org/wiki/Chi-squared_distribution

    Because the square of a standard normal distribution is the chi-squared distribution with one degree of freedom, the probability of a result such as 1 heads in 10 trials can be approximated either by using the normal distribution directly, or the chi-squared distribution for the normalised, squared difference between observed and expected value.

  9. Multivariate normal distribution - Wikipedia

    en.wikipedia.org/wiki/Multivariate_normal...

    The null hypothesis is that the data set is similar to the normal distribution, therefore a sufficiently small p-value indicates non-normal data. Multivariate normality tests include the Cox–Small test [ 33 ] and Smith and Jain's adaptation [ 34 ] of the Friedman–Rafsky test created by Larry Rafsky and Jerome Friedman .