Repeated records need different actions
The same ID can appear more than once for several reasons. The correct action depends on what the rows mean.
Confirmed copy: remove the extra copy for a current registry. Verified correction: use the authoritative revision and retain the earlier record in the audit history. Unresolved conflicting values: flag and investigate rather than arbitrarily taking the first or latest. Repeated observations: retain different weeks, courses or events and use the appropriate composite key.
'Keep the latest' is justified only when the timestamp and source process identify a genuine superseding correction. A later upload can be stale information, a different event or a less authoritative source.
Worked W3 question, PDF p. 21: after removing the confirmed copy, Biology contains a score of 70 and an unresolved score of either 60 or 80. Candidate Biology means are 65 and 75. Reporting 75 as settled is unjustified until the conflicting version is verified. Bioengineering's 90 belongs to a different programme.
Source: W3 PDF pp. 4-55. The 14-row registry example below comes from the Week 3 lab code you previously pasted in this conversation; it is separate from the lecture's smaller examples.
The lecture distinguishes copies, corrections and repeated events. The evidence packet supports removing R13, retaining R14 over R02, and flagging an invalid age value.
Practice problems
Supplementary study questions on the lecture concepts — not verbatim exam questions. Each answer counts toward spaced review.
1. Conceptual understanding
Definitions and distinctions.
When is retaining the latest record justified here?
Two rows describe the same student in weeks 1 and 2. What should you do?
2. Application
Apply the concept to a case or calculation.
R13 is confirmed as an extra export copy of R01. Which action fits a current registry?
Why retain R14 instead of R02 in this lab?
3. Interpretation and limitations
Evaluate assumptions and justify conclusions.
Two unverified scores are 60 and 80. Which mean claim is safest?
Deleting week 1 and keeping week 2 loses what?
Explain it in writing
Self-checked, not marked. Write a few sentences, then compare with the example answer. Your writing is saved as you type.
Show an example answer
Flag the conflict and check the authoritative student-and-exam source. Do not silently choose the later or higher value as settled truth.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?
Show an example answer
One row represents one student's assessment in one week, under the stated course/assessment context. Use student_id plus week and any additional course or assessment identifier needed for uniqueness.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?