Rule of Context
Quantities carry the context needed to interpret them.
Requirement
A quantitative claim must identify its measure, units, applicable period, and population or scope. Rates must identify their denominator; performance comparisons must identify their baseline. Currency must be unambiguous. Source information must be accessible, with freshness stated when it affects the decision.
Why
A precise-looking number can still be uninterpretable or incomparable.
Application
Put essential context beside the value or in a clearly shared heading. Do not hide essential units or periods exclusively in hover content. Shared context can cover a whole table or chart group; repeating it in every cell adds noise. Detailed source documentation may be expandable.
Examples
The pair isolates this rule. A good example is not approval of the entire interface.
Good for this task
7.2% is labeled as late-delivery rate, last 30 days, Ground parcels, with the denominator and source available.
Late-delivery rate
Bad for this task
A large 7.2% KPI appears without measure, period, population, or denominator.
Late-delivery rate
These synthetic fixtures illustrate the stated comparison. Native checks can support review of declared scales, context, encodings, geometry, and legibility; they do not establish data truth or task relevance. Review the requirement and exceptions above.
Enforcement
automated is the strongest mechanism Viewrule expects for the complete rule. Partial checks can still provide supporting evidence without proving the whole requirement.