A percentage says how one amount relates to another. Without the denominator, the reader may not know whether the figure describes all visitors, completed tasks, or a selected subset.

Write the group beside the percentage and check whether that group changed between comparisons. A rising share can happen while the underlying count falls if the total falls more. Counts and proportions answer related but different questions.

When comparing percentages, distinguish a change in percentage points from a relative percentage change. State the starting value and the method of comparison. A clear denominator gives a small number enough context to carry an accurate explanation.

A few starting points
  1. Name the group behind the percentage.
  2. Compare counts as well as shares.
  3. Distinguish percentage points from relative change.

Imagine a practical setting.

Imagine two groups completing different numbers of attempts. A completion count alone cannot establish the same comparison as a rate with its total shown.

Before the next experiment.

Keep the question beside the number. A measure is easier to interpret when the reader knows which decision or comparison it was intended to support.

Follow a related question

Identify which material is actually included.

Context is an input with a boundary

Compare the same subject under different light.

Light becomes a digital picture

Keep learning

Related background to continue exploring this subject.

NIST: statistical engineering NIST: the International System of Units
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