MEPX
Chapter 3 of 13All chapters
  1. 1What analysis is for
  2. 2Types of data
  3. 3Collecting and sampling
  4. 4Cleaning data
  5. 5Describing the middle
  6. 6Describing the spread
  7. 7Choosing a chart
  8. 8Correlation
  9. 9Getting to causation
  10. 10Hypothesis testing
  11. 11Traps and paradoxes
  12. 12Tools of the trade
  13. 13Communicating results

Chapter 3 of 13

Collecting and sampling

Where the answer is usually decided.

Representativeness

A sample describes the group it was drawn from, not the group you meant. A survey answered only by enthusiasts describes enthusiasts, however many replied.

  • Random selection is what makes a sample generalisable; size alone does not.
  • Non response is a form of bias: the people who ignored you may differ systematically.

Survivorship

Looking only at what made it through distorts everything. Studying successful companies tells you what successes look like, not what causes success, because the failures did the same things.