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  2. Off-by-one error - Wikipedia

    en.wikipedia.org/wiki/Off-by-one_error

    Off-by-one errors are common in using the C library because it is not consistent with respect to whether one needs to subtract 1 byte – functions like fgets() and strncpy will never write past the length given them (fgets() subtracts 1 itself, and only retrieves (length − 1) bytes), whereas others, like strncat will write past the length given them.

  3. Listwise deletion - Wikipedia

    en.wikipedia.org/wiki/Listwise_deletion

    Because listwise deletion excludes data with missing values, it reduces the sample which is being statistically analysed. Listwise deletion is also problematic when the reason for missing data may not be random (i.e., questions in questionnaires aiming to extract sensitive information. [ 3 ]

  4. Missing data - Wikipedia

    en.wikipedia.org/wiki/Missing_data

    The expectation-maximization algorithm is an approach in which values of the statistics which would be computed if a complete dataset were available are estimated (imputed), taking into account the pattern of missing data. In this approach, values for individual missing data-items are not usually imputed.

  5. Secretary problem - Wikipedia

    en.wikipedia.org/wiki/Secretary_problem

    That is, the interviewer will derive some value from selecting an applicant that is not necessarily the best, and the derived value increases with the value of the one selected. To model this problem, suppose that the n {\displaystyle n} applicants have "true" values that are random variables X drawn i.i.d. from a uniform distribution on [0, 1].

  6. Quartile - Wikipedia

    en.wikipedia.org/wiki/Quartile

    The values of can be found with the quantile function where = for the first quartile, = for the second quartile, and = for the third quartile. The quantile function is the inverse of the cumulative distribution function if the cumulative distribution function is monotonically increasing because the one-to-one correspondence between the input ...

  7. Kernel density estimation - Wikipedia

    en.wikipedia.org/wiki/Kernel_density_estimation

    Kernel density estimate (KDE) with different bandwidths of a random sample of 100 points from a standard normal distribution. Grey: true density (standard normal). Red: KDE with h=0.05. Black: KDE with h=0.337. Green: KDE with h=2. The bandwidth of the kernel is a free parameter which exhibits a strong influence on the resulting estimate.

  8. Correlation - Wikipedia

    en.wikipedia.org/wiki/Correlation

    Moreover, the correlation matrix is strictly positive definite if no variable can have all its values exactly generated as a linear function of the values of the others. The correlation matrix is symmetric because the correlation between X i {\displaystyle X_{i}} and X j {\displaystyle X_{j}} is the same as the correlation between X j ...

  9. Mean absolute percentage error - Wikipedia

    en.wikipedia.org/wiki/Mean_absolute_percentage_error

    It is a measure used to evaluate the performance of regression or forecasting models. It is a variant of MAPE in which the mean absolute percent errors is treated as a weighted arithmetic mean. Most commonly the absolute percent errors are weighted by the actuals (e.g. in case of sales forecasting, errors are weighted by sales volume). [3]