MEPX
Chapter 4 of 10All chapters
  1. 1The method
  2. 2Designing an experiment
  3. 3When you cannot experiment
  4. 4Measurement
  5. 5Reading a result
  6. 6Hypotheses, theories and laws
  7. 7How science is published
  8. 8Replication
  9. 9Telling it apart
  10. 10Using it yourself

Chapter 4 of 10

Measurement

Getting numbers that mean something.

Valid and reliable

Reliable means repeatable; valid means it measures what you claim. A scale that reads two kilograms heavy every time is perfectly reliable and useless.

  • Every instrument has error, and reporting it is part of the result.
  • Proxy measures drift: what is easy to measure replaces what matters.

Significant figures

Precision beyond what the instrument supports is a false claim. Carrying ten digits from a two-digit measurement is a common way to mislead without lying.