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4-12 Outliers and choosing the right measure

4-12 Outliers and choosing the right measure

Point 12 of 12 — Unit 4: Statistics — Measures of DispersionQuestion bank: 0 questions (0 with pictures)

12 4-12 Outliers and choosing the right measure

  • An outlier is a value far removed from the rest; it drags the mean and inflates the standard deviation and the range, but barely affects the median and the IQR.
  • A common test flags a value as an outlier if it lies below Q1 − 1.5 × IQR or above Q3 + 1.5 × IQR.
  • When an outlier is present (or the distribution is heavily skewed), report the median with the IQR; otherwise the mean with the standard deviation is the better pair.
  • Never delete an outlier silently: either justify its removal (measurement error) or keep it and switch to the robust measures.

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