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Grade 3 · lesson 3 of 4

Protect One Record per Observed Item

Check the identifier under the stated one-row-per-item policy.

About 18 minutes, plus any extended practice

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Supplied materials

  • Paper and pencil; answers may also be spoken or typed.
  • All cases, labels, numbers and rules are supplied on this page. No real account, private information or purchase is needed.

Learn the idea

A record should represent the stated unit, such as one item or one observation. Repeated item IDs may indicate accidental duplicates, but repeated observations can also be legitimate when dates differ. The supplied policy says one row per item for this single check. Apply that policy rather than deleting every repeated value.

Check the identifier under the stated one-row-per-item policy. Equal counts in different items are not duplicate records.

Use this supplied case: ID A appears once. Policy: one row per item. Classify the record. Use the details in this example. Say which detail helped you choose. This pretend example does not tell us how every real system works.

  1. Follow the worked example one step at a time. Say or draw what happens.
  2. Check the identifier under the stated one-row-per-item policy.
  3. Say which detail makes the example answer fit. Pick another answer and say why it does not fit.
  4. Try the question and practice questions. Read the rule again if your answer does not match the explanation.
Worked example

See the method in action

The entire supplied record is one row, ID L/count 5. Under one-row-per-item policy, the present ID appears once: this is one identified item record. Compare rows ID M/count 6 and ID N/count 6. Their counts match, but M≠N, so they represent distinct identified items. By contrast, two rows both bearing ID P repeat that item ID. Check identifiers before treating equal measurement values as duplicates.

Your turn

Check your reasoning

Your answer is temporary and is not saved to an account. Download your current answer before leaving or reloading. Written work on paper or in another app stays in your own file.

Helpful tips
  • Check the identifier under the stated one-row-per-item policy.
  • Equal counts in different items are not duplicate records.
Supplied rows have item IDs B and B. Policy: one row per item. Which identity condition is shown?

Feedback appears here after you check. This is practice, not a graded school assessment.

See the answer and explanation

The same item ID is repeated

ID B occurs in two rows, violating the stated one-row-per-item rule. This record gives no different ID or missing-ID case.

Take it further

Policy now allows one observation per item per day. ID A on day 1 and day 2 is not automatically a duplicate; two identical ID A/day 1 rows need investigation.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.

More practice: try new cases

Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.

More practice: try new cases
1. A single supplied row has a blank item ID. Policy: every row needs an ID and each item appears once. Which identity condition is shown?
Need a hint?
  • Use the explicit input, condition and question aspect.
  • Reject a choice that adds an unsupported condition or answers a different question.
2. The two supplied rows are ID C/count 4 and ID D/count 4. Policy: one row per item. What do the equal counts show?
Need a hint?
  • Use the explicit input, condition and question aspect.
  • Reject a choice that adds an unsupported condition or answers a different question.
3. One check has two rows for item ID E. Policy: one row per item in this check. Which identity condition is shown?
Need a hint?
  • Use the explicit input, condition and question aspect.
  • Reject a choice that adds an unsupported condition or answers a different question.

Your choices are temporary. Feedback appears after you check all the answers.

Nothing here is saved to an account or sent to a teacher. Keep your own notes or download them before leaving. The score describes these questions; it does not certify subject mastery.

Check the subject sources

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.