Outliers
Values that are significantly different from the rest of the dataset. Formally, a value x is an outlier if x < Q₁ - 1.5×IQR or x > Q₃ + 1.5×IQR.
Real World
When Spotify analyses daily streaming counts, a track going viral after a TikTok trend might register as an outlier, flagging the data science team to investigate whether it reflects genuine popularity or bot activity.
Exam Focus
Show the full outlier calculation (Q1 − 1.5×IQR or Q3 + 1.5×IQR) before stating whether a value is an outlier.
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