2.3 We Have a Problem

The sample is not the population!

The sample statistics we calculate are not equal to the population statistics!

The sample statistic may differ from the population statistic for a variety of reasons:

• random fluctuation
• bias
  • selection bias (the sample may not have been drawn randomly from the population)
  • sample size bias³ (some sample metrics will be inherently and systematically different from population metrics just because of the limited size of the sample)

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3. the book glosses over this, so I don’t know if there’s a more standard term than just “bias”↩︎