The idea, step by step
Who collected it, and why?
Primary data are newly collected first-hand for the current study, such as your measurements of seedlings. Secondary data already exist and are reused, such as a published rainfall table. The classification depends on the user and purpose. Your own survey is primary for your study; a friend reusing it for a different project uses secondary data.
Check usefulness and protect people
Record the producer, date, location, units, definitions and sampling method. Old or differently defined data may not answer a current question. Secondary does not mean unreliable. Do not publish identifying names merely because they occur in the source; use anonymous records or suitable summaries, and report missing metadata instead of guessing.
A common trap
Secondary data are always less reliable.
Instead: Collection quality and suitability determine usefulness, not merely who reuses the data.
See the thinking
Worked example 1
Mira records her own rain gauge for a project and reuses a published rainfall table. Classify each.
- Her direct project measurements are primary.
- The already existing table is secondary for her project.
Worked example 2
A table lists 12,15,18 but no units, dates or description. Can it establish this week’s bus waits?
- The quantities may not be minutes.
- Location and collection period are unknown.
- Definitions and source information must be checked.
Check your understanding
You interview members for your own new club study. Primary or secondary?
Show answer
Primary.
You collect the responses directly for this purpose.
Your turn
6 questions · 11 marks · Work at your own pace.
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 ↗