lesson
Completeness and accuracy are different
1 · Learn
A dataset can have every field filled yet contain incorrect values. It can also contain accurate observed values but omit important cases. Assess accuracy, completeness, consistency and relevance separately.
Document missing-data decisions instead of silently inventing replacements. A valid format does not establish that a value was measured correctly.
2 · Worked example
A date formatted correctly can still be the wrong date. A complete attendance table can still exclude a class entirely.
3 · Your turn
Does every cell being non-empty prove a dataset is accurate?
Check your answer
No. Filled cells can contain wrong or fabricated values.
4 · Apply your learning
Audit a small invented table and classify each issue rather than calling every issue simply 'bad data'.
Adult guidance and safety
Use an approved sandbox, invented data and test accounts. Do not probe other systems or expose credentials. Retain test evidence and accessibility checks; these teaching models are not a completed practical project or a specified GCSE qualification.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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