Understand the idea.
Who collected it, and why?
Primary data are collected first-hand for the current investigation, such as your own seedling measurements. Secondary data already exist and are reused, such as a published rainfall table. Ask who collected the information and for which study.
The same records can have different roles for different users. Your new survey responses are primary for your investigation; a friend who later reuses those records for another project is using secondary data. The label describes the collection relationship, not quality.
Check usefulness and protect people
Before using a source, check its producer, collection date, place, units, definitions and sampling method. A reliable table can still be unsuitable if its measurements concern a different period or group. Missing information must be checked rather than filled in by guessing.
Protect the people behind the data. Use anonymous records or summaries when names are unnecessary, and collect only what the investigation needs. Published information is not automatically suitable to republish with identifying details; the report should explain source limitations as well as results.
See the method in action.
Worked example 1
Mira records her own rain gauge for a project and reuses a published rainfall table. Classify each.
Worked solution
- 1
Examine Mira's rain-gauge readings.
Mira collects these measurements herself for her current project, so they are primary data.
- 2
Examine the published rainfall table.
The table existed before Mira reused it, so it is secondary data for her project.
- 3
Keep classification separate from quality.
Both sources still need checks of measurement method, place and period before they can support a comparison.
Gauge readings: primary; reused table: secondary.
Worked example 2
A table lists 12,15,18 but no units, dates or description. Can it establish this week’s bus waits?
Worked solution
- 1
Check what the numbers measure.
The values 12, 15 and 18 have no units or description, so they cannot yet be interpreted as waiting times in minutes.
- 2
Check whether they concern the required week.
No dates or location are supplied, so the figures may describe another place, period or quantity.
- 3
State the justified conclusion.
They cannot establish this week's bus waits until their source, definitions, units and collection details are verified.
No justified conclusion is possible yet.
Try it yourself.
Check your understanding
You interview members for your own new club study. Primary or secondary?
Show answer & reasoning
Primary.
You obtain the interview responses directly for this new club investigation, so the responses are primary data for your study.
Keep practising
6 worksheet questions · 11 marks
Read the questions online
- You reuse a published census table. Classify the source for your project.1 mark
- You measure 12 seedlings grown for your study. Classify the source.1 mark
- You use a friend’s class survey from last year in a new project. Classify it.2 marks
- A travel-time graph lacks vertical-axis units. What must you establish?2 marks
- A current Year 8 question uses Year 12 data collected five years ago. Give two suitability concerns.2 marks
- A source includes names and journey times. What should a public report use instead?3 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- You reuse a published census table. Classify the source for your project.1 mark
The data already exist.
Secondary. - You measure 12 seedlings grown for your study. Classify the source.1 mark
You collect measurements first-hand for the study.
Primary. - You use a friend’s class survey from last year in a new project. Classify it.2 marks
It was collected previously for another purpose.
Secondary. - A travel-time graph lacks vertical-axis units. What must you establish?2 marks
Numbers have different meanings with different units.
Whether values are seconds, minutes, hours or another defined unit. - A current Year 8 question uses Year 12 data collected five years ago. Give two suitability concerns.2 marks
Age/year level and changing conditions may both matter.
Different group and different period. - A source includes names and journey times. What should a public report use instead?3 marks
Protect the identities of participants.
Anonymous times or suitable summaries without names.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum
Population, census and sample; observational versus experimental data; random and non-random sampling; primary/secondary data; reviewing numerical displays and summary statistics; comparing samples and sample sizes; bias, variation and uncertainty; planning, conducting and reporting a fair investigation.
Official curriculum source ↗