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Reading & writing · Grades 9–12

Reading numerical claims critically

A percentage needs a base group and a clear time period.

Make a worksheet

Understand the idea

Check denominators

A percentage needs a base group and a clear time period.

Compare like with like

Definitions, scales, sampling methods and uncertainty affect a comparison.

Examples and reasoning

A rate rises from 2% to 3%. The increase in percentage points is

1 percentage point

1 percentage point

A rate rises from 2% to 3%. The relative percentage increase is

50%

50%

Check your understanding

  1. A headline says incidents doubled but omits counts. Which extra fact matters?

    1. the original and new incident counts
    2. the headline font only
    3. the reporter’s favourite colour
    4. the number of syllables

  2. A bar chart starts its vertical axis at 95 rather than 0. What should a reader check?

    1. Whether numbers can be ignored.
    2. Whether the truncated scale exaggerates visual differences.
    3. Whether all data are automatically false.
    4. Whether colours prove causation.

  3. Which sampling approach is least obviously self-selected?

    1. randomly contacting a defined sample
    2. collecting only positive reviews
    3. an optional poll on a fan page
    4. asking friends who agree

  4. Explain why an average can hide differences within a group.

Answers and marking notes

Answers and marking notes
  1. the original and new incident counts

    the original and new incident counts

  2. Whether the truncated scale exaggerates visual differences.

    Whether the truncated scale exaggerates visual differences.

  3. randomly contacting a defined sample

    randomly contacting a defined sample

  4. Different distributions or unequal subgroup outcomes can produce the same average.

    Different distributions or unequal subgroup outcomes can produce the same average.

Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.