3 ms·

Neatly phrased: Trends which appear in slices of data may disappear or reverse when the groups are combined.

• naasking 8y ago
  Or perhaps even more succinctly: slicing data can introduce bias.
  • Matumio 8y ago
    This is less accurate, because not slicing data can also lead to bias.
    • naasking 8y ago
      Except the original statement didn't make any claim about "not slicing", so neither does mine.
      • throway88989898 8y ago
        Not slicing is nevertheless slicing. The trivial selection. Rush's song "If you choose not to decide you still have made a choice"