Understand the idea.
What kind of answer will you collect?
Begin with the question being asked. Favourite fruit asks for a name, so it gives category data. Number of books asks for a count; height asks for a measurement. Both counts and measurements give number data.
Look at what a number means before classifying it. Bus route names a route; it does not count seven buses. Adding two route labels would not tell us a useful total, but adding counts of books would.
Check before using the records
Validation means checking whether records fit the question. Check the units, look for missing answers and investigate values that seem surprising. A missing height is not zero, and an unusually tall plant is not automatically a recording mistake.
Totals provide another check. The fruit counts give votes. If each of pupils gave one answer but the total were , compare the counts with the original responses before changing anything.
| Fruit | Votes |
|---|---|
| Apples | 8 |
| Bananas | 6 |
| Oranges | 4 |
| Pears | 2 |
See the method in action.
Numbers used as labels
Classify favourite game, number of pets and bus route number.
Worked solution
- 1
Classify favourite game as category data.
A response names a choice of game rather than counting or measuring something.
- 2
Classify number of pets as number data.
Each response counts how many pets a person has, so the counts can be meaningfully totalled.
- 3
Classify bus route number as category data.
The numeral identifies a route; it does not describe the quantity of buses.
Category; number; category.
An entry to check
Plant heights are recorded as 8, 9, 85, 10, 9 centimetres. What should happen before graphing?
Worked solution
- 1
Identify the measurement needing investigation.
The recorded height of is much larger than the other four measurements.
- 2
Check the original record, unit and plant.
The plant may really be taller, or there may be a unit or recording error; remeasurement can help distinguish these.
- 3
Correct a mistake only if the check supplies evidence.
Changing to without evidence would replace a recorded measurement with a guess; record any confirmed correction.
Check 85 and its unit. Do not guess that it should be 8.5.
Try it yourself.
Check your understanding
Is the number of library books borrowed category data or number data?
Show answer & reasoning
Number data: it is a count.
The number borrowed is number data because it counts books. A response of means four books, and counts from different borrowers can be added to find a total.
Keep practising
6 worksheet questions · 9 marks
Read the questions online
- Classify favourite sandwich filling as category data or number data.1 mark
- Classify the length of a pencil in centimetres.1 mark
- Classify a football player's shirt number.1 mark
- A survey has 18 answers. Category counts are 6, 5 and 8. What needs checking?2 marks
- Reading times are recorded as 4 hours, 5 hours and 300 minutes. Explain why the units matter.2 marks
- A data sheet has a blank height. Should it be entered as zero? Explain.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Classify favourite sandwich filling as category data or number data.1 mark
The answer names a kind of filling.
Category data. - Classify the length of a pencil in centimetres.1 mark
Length is a measurement with a unit.
Number data. - Classify a football player's shirt number.1 mark
It identifies a player; it does not measure the player.
Category data. - A survey has 18 answers. Category counts are 6, 5 and 8. What needs checking?2 marks
.
Check for an extra or double-counted response; do not remove one without evidence.
The counts total 19, one more than the 18 answers. - Reading times are recorded as 4 hours, 5 hours and 300 minutes. Explain why the units matter.2 marks
There are 60 minutes in an hour.
.
Use one agreed unit before comparing; 300 minutes equals 5 hours. - A data sheet has a blank height. Should it be entered as zero? Explain.2 marks
Check or remeasure if possible.
If it cannot be obtained, label the measurement missing.
No. A missing measurement is not a measured height of zero.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum 2026
Data types/validation; mode; suitable displays; line graphs; statistical investigations.
Official curriculum source ↗