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  2. Probability density function - Wikipedia

    en.wikipedia.org/wiki/Probability_density_function

    Probability density function. Box plot and probability density function of a normal distribution N(0, σ2). Geometric visualisation of the mode, median and mean of an arbitrary unimodal probability density function. [1] In probability theory, a probability density function (PDF), density function, or density of an absolutely continuous random ...

  3. Median - Wikipedia

    en.wikipedia.org/wiki/Median

    The median of a normal distribution with mean μ and variance σ 2 is μ. In fact, for a normal distribution, mean = median = mode. The median of a uniform distribution in the interval [a, b] is (a + b) / 2, which is also the mean. The median of a Cauchy distribution with location parameter x 0 and scale parameter y is x 0, the location parameter.

  4. Mode (statistics) - Wikipedia

    en.wikipedia.org/wiki/Mode_(statistics)

    For the music theory concept of "modes", see Mode (music). In statistics, the mode is the value that appears most often in a set of data values. [ 1 ] If X is a discrete random variable, the mode is the value x at which the probability mass function takes its maximum value (i.e., x=argmaxxi P (X = xi)). In other words, it is the value that is ...

  5. Chi-squared distribution - Wikipedia

    en.wikipedia.org/wiki/Chi-squared_distribution

    The chi-squared distribution is one of the most widely used probability distributions in inferential statistics, notably in hypothesis testing and in construction of confidence intervals. [3][4][5][6] This distribution is sometimes called the central chi-squared distribution, a special case of the more general noncentral chi-squared distribution.

  6. Symmetric mean absolute percentage error - Wikipedia

    en.wikipedia.org/wiki/Symmetric_mean_absolute...

    (200% for the first formula and 100% for the second formula). Provided the data are strictly positive, a better measure of relative accuracy can be obtained based on the log of the accuracy ratio: log( F t / A t ) This measure is easier to analyse statistically, and has valuable symmetry and unbiasedness properties.

  7. Probability distribution - Wikipedia

    en.wikipedia.org/wiki/Probability_distribution

    A probability distribution is a mathematical description of the probabilities of events, subsets of the sample space. The sample space, often represented in notation by is the set of all possible outcomes of a random phenomenon being observed. The sample space may be any set: a set of real numbers, a set of descriptive labels, a set of vectors ...

  8. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    Probability theory. In probability theory and statistics, a normal distribution or Gaussian distribution is a type of continuous probability distribution for a real-valued random variable. The general form of its probability density function is The parameter is the mean or expectation of the distribution (and also its median and mode), while ...

  9. Interquartile range - Wikipedia

    en.wikipedia.org/wiki/Interquartile_range

    In descriptive statistics, the interquartile range (IQR) is a measure of statistical dispersion, which is the spread of the data. [1] The IQR may also be called the midspread, middle 50%, fourth spread, or H‑spread. It is defined as the difference between the 75th and 25th percentiles of the data. [2][3][4] To calculate the IQR, the data set ...