Quality means fitness for the task
A field can be important for one task and irrelevant to another. Judge whether the needed information is complete, sensible and trustworthy.
A blank phone number prevents an urgent phone call. It does not prevent counting a known programme or analysing an available score. Judge quality relative to the intended task, rather than treating every incomplete row as useless.
| Dimension | A concrete question or check |
|---|---|
| Completeness | Are expected records and required cells present? Compare with a roster as well as counting blanks. |
| Validity | Does each value satisfy the documented type, category, range or format? |
| Consistency | Do related fields and representations agree, such as start before end and approved programme aliases? |
| Uniqueness | Is the intended key unique at the stated row grain? |
| Accuracy | Does the stored value agree with the correct measurement for that person and event? |
| Timeliness | Is the information current enough for this purpose, considering event time and snapshot time? |
A score of 67 and a score of 76 both pass a 0-100 range check. If the marked exam records 76, only the second is accurate. Assertions cannot establish a source fact they never check. A timestamp says when something was updated, not that a phone number still works.
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 six quality dimensions are applied to a concrete task. The dictionary decides the score scale, date order and allowed programme meanings.
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.
A score 67 passes a 0–100 check, but the exam sheet says 76. What is wrong?
A phone is blank but programme is known. For programme counts, what should happen?
2. Application
Apply the concept to a case or calculation.
Which check directly looks for absent expected students?
A score 150 violates a documented 0–100 scale. Which dimension is directly affected?
3. Interpretation and limitations
Evaluate assumptions and justify conclusions.
Approved aliases 'BIO' and ' biology ' represent the same programme. What improves consistency?
A phone was updated last month. What does that prove?
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
Check whether a later authoritative record changed the information. For an urgent call, verify that the phone number is still usable; an update date alone is insufficient.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?
Show an example answer
Consistency concerns agreement between representations or related fields. Uniqueness concerns whether the intended key appears only once at the chosen row definition.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?