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  • Jia Wu Wu

    August 30, 2020 at 8:06 pm

    two common ways to identify outliers:

    1.Upper control limit (UCL) and lower control limit (LCL), calculated by mean and standard deviation (std) of the sample

    UCL = mean + 3 * std

    LCL = mean - 3 * std

    Anything outside of the range can be treated as outliers.

    2. Quartiles, calculated by median (instead of mean), and needs to sort the sample

    Q1, 25%, the middle number between the smallest number and median

    Q2, 50%, the median

    Q3, 75%, the middle number between the median and the largest number

    IQR(Interquartile range) = Q3-Q1

    Upper limit = Q3 + 1.5 * IQR

    Lower limit = Q1 - 1.5 * IQR

    Anything outside of the limits can be considered outliers