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Grade 12 · lesson 2 of 4

Aggregate Only the Required Events

Build daily failure counts from fictional records and drop unnecessary fields.

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Supplied materials

  • Paper and pencil; an adult may read aloud. No device, account or purchase is needed.

Learn the idea

Data minimization starts with a specific purpose and asks what is necessary to achieve it. Our purpose is internal daily failure counts by activity code. Individual histories, names and answer text do not help answer that count question. An aggregate reduces detail, but the context and small groups can still create privacy risks.

Fictional input records contain day, activity and outcome only: (D1,A,fail), (D1,A,pass), (D1,B,fail), (D1,A,fail), (D2,A,fail). Algorithm: start an empty count table; for each fail event, add 1 to the group keyed by (day,activity); ignore pass events; retain only the aggregate rows. Here absent groups mean zero failures, not unknown data.

  1. State the purpose and three permitted input fields.
  2. Trace the count table after each of the five supplied events.
  3. Return groups (D1,A), (D1,B) and (D2,A), with their counts.
  4. Explain why adding full_name or typed_answer is unnecessary for this purpose and why aggregate output still needs controlled access.
Worked example

See the method in action

Aggregate output: (D1,A,2), (D1,B,1), (D2,A,1). Four fail events are counted and one pass event is ignored. No person identifiers or answer text are retained in the exercise output.

Your turn

Check your reasoning

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Append (D2,A,pass) and (D2,B,fail). What are the failure counts for D2 A and B?

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See the answer and explanation

A = 1, B = 1

The new pass does not increment D2 A. The new fail creates D2 B with count 1, so both D2 groups have count 1.

Take it further

Change the purpose to daily total check counts by activity, including passes. Expected original-data counts: D1 A = 3, D1 B = 1, D2 A = 1. The aggregation condition changes; names and answers are still unnecessary for the stated totals.

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These LifeStarter passages, scenarios and exercises are authored for this Academy with AI assistance and review. External resources keep their publishers’ terms. A grade label suggests a starting level; it does not establish alignment with your school’s complete requirements.