Base Rates and Denominators

Objectives

Ask what the denominator is
Recognize a numerator presented alone

Video

Data & Infographics. Crash Course · Navigating Digital Information #8. Watch on YouTube

Lesson

A count without a population is an impression. Ten incidents matter differently in a town of five hundred than in a city of a million. A rise in reports can reflect more reporting rather than more events.

When a number arrives without its denominator, the missing denominator is the story. Ask what a complete sample would show before drawing the conclusion the number invites.

Terms

Observation, Assessment

Sources

bjs.ojp.gov (opens in a new tab)

Check

- The reporter’s opinion
- The denominator
- A second headline
- Nothing; names are enough
- The counting-rule change, until it is checked
- The jump proves the policy worked
- The jump proves the policy failed
- Retire the counting rule and publish the jump
- Unknown. Cannot be determined from the record.
- The population those ten incidents were drawn from
- A second anecdote that makes the count feel more real
- The name of the person who compiled the ten incidents
- A chart, so the count can be seen instead of read