← Module 5: Scientific Investigations
Inquiry Question 1: What are the steps and considerations necessary to plan and conduct a scientific investigation?
Plan, source and acknowledge primary and secondary data appropriate to the investigation
A focused answer to the HSC Investigating Science Module 5 dot point on primary and secondary data. Covers the distinction, sourcing and acknowledging secondary data, evaluating source quality, and worked HSC past exam questions.
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What this dot point is asking
NESA wants you to define primary and secondary data, identify which is appropriate for a given investigation, and evaluate the reliability of secondary data sources. Source evaluation is examined every year because it underpins evidence-based reasoning.
The answer
Scientific investigations use two distinct types of data, and most strong investigations combine them.
Primary data
Data collected directly by the investigator through observation, measurement, experiment or survey. The investigator controls how the data is gathered.
Examples.
- A student measures the pH of soil samples from three sites.
- A CSIRO scientist records seabird counts on Lord Howe Island.
- A clinical trial team measures patient outcomes in a new drug trial.
Strengths. Targeted to the investigator's hypothesis, full control over methodology, known provenance.
Limitations. Limited by the investigator's time, budget, equipment and access. Cannot retrospectively gather historical data.
Secondary data
Data collected by other researchers and accessed through published sources. The investigator did not gather the data themselves.
Examples.
- Bureau of Meteorology climate records dating back over a century.
- ABS census data on Australian population demographics.
- Peer-reviewed journal articles reporting laboratory measurements.
- AIHW health statistics (Australian Institute of Health and Welfare).
- Genome databases such as NCBI GenBank.
Strengths. Allows investigation of large-scale patterns, long time series, rare events or expensive measurements the investigator cannot replicate. Provides context for primary findings.
Limitations. The investigator did not control the methodology and must rely on the original researchers' reported methods. Risk of unreliable or biased sources if not evaluated carefully.
Sourcing secondary data
Trusted Australian sources for HSC investigations:
- CSIRO (csiro.au): peer-reviewed and government-vetted research.
- Bureau of Meteorology (bom.gov.au): authoritative climate and weather data.
- Australian Bureau of Statistics (abs.gov.au): population and economic data.
- Australian Institute of Health and Welfare (aihw.gov.au): national health statistics.
- NHMRC (nhmrc.gov.au): medical research guidelines and outcomes.
- PubMed and Google Scholar: peer-reviewed biomedical literature.
Acknowledging sources
Every secondary source used in an investigation must be cited. Standard formats include:
- APA referencing for journal articles: Author, A. (Year). Title. Journal, Volume(Issue), Pages.
- In-text citation when paraphrasing or quoting.
- Bibliography or reference list at the end of the report.
Failure to acknowledge sources is academic misconduct and a form of intellectual theft.
Evaluating secondary data quality
The CRAAP test (or similar) is the standard framework.
| Criterion | What to check |
|---|---|
| Currency | When was it published? Is current data relevant? |
| Relevance | Does it answer the inquiry question directly? |
| Authority | Who is the author? What is their expertise and institution? |
| Accuracy | Is the methodology described? Was it peer reviewed? |
| Purpose | Why was it written? Is there a conflict of interest? |
Worked example of combined use
Investigating drought trends in the Murray-Darling Basin:
- Primary data. A student measures rainfall, soil moisture and vegetation cover at a single site over three months.
- Secondary data. BOM rainfall records for the basin from 1900 to 2024, MDBA water-level data, peer-reviewed papers on climate-driven streamflow change.
The primary data anchors the investigation in real measurements; the secondary data provides historical context and the scale required to detect long-term trends.
Past exam questions, worked
Real questions from past NESA papers on this dot point, with our answer explainer.
2022 HSC4 marksDistinguish between primary and secondary data, and explain why both are necessary in scientific investigation.Show worked answer →
A 4-mark answer needs definitions, examples, and a reason why both are required.
- Primary data
- Data collected directly by the investigator through observation, measurement or experiment. Example: a student measures the rate of photosynthesis using elodea pondweed in their classroom.
- Secondary data
- Data collected by other researchers and accessed through published sources such as journal articles, government reports, databases or textbooks. Example: a student uses Bureau of Meteorology temperature records from 1900 to 2024 to investigate climate trends.
- Why both are necessary
Primary data is essential for testing a specific hypothesis under conditions the investigator controls, and for producing first-hand evidence.
Secondary data is essential for contextualising findings, drawing on data the investigator cannot generate (long time series, large samples, expensive instruments) and avoiding wasted duplication of effort.
Most real scientific investigations combine both. Climate science depends on primary measurements at weather stations combined with secondary historical archives. Medical research combines primary trials with secondary meta-analysis.
Markers reward both definitions, an example for each, and an explicit reason both are used together.
2024 HSC3 marksList three criteria you would use to evaluate the reliability of a secondary data source.Show worked answer →
A 3-mark answer needs three distinct criteria with brief explanation.
Authority and expertise. Is the source from a qualified scientist, a peer-reviewed journal, a government agency such as CSIRO or the Bureau of Meteorology, or an established research institution? Wikipedia and blogs are not primary sources and require cross-referencing.
Peer review and methodology. Was the work peer-reviewed before publication? Does the source describe the methodology in enough detail that another researcher could replicate it? Reliable sources show their working.
Currency and conflict of interest. Is the data current and relevant to the investigation? Is the source free from undisclosed funding bias (for example, tobacco industry-funded research on smoking, or fossil-fuel-funded climate research)? Disclosure of conflicts is essential.
Other valid criteria include corroboration with other independent sources, reputation and citation count of the publishing journal, and statistical robustness. Markers reward three distinct criteria with reasoning.
Related dot points
- Develop and evaluate questions and hypotheses for scientific investigation
A focused answer to the HSC Investigating Science Module 5 dot point on inquiry questions and hypotheses. Covers what makes a question testable, the difference between a hypothesis and a prediction, falsifiability, and worked HSC past exam questions.
- Communicate scientific understanding using suitable language and terminology, including the role of peer review and replication in confirming scientific findings
A focused answer to the HSC Investigating Science Module 5 dot point on peer review and replication. Covers what peer review does, why it matters, the reproducibility crisis, and worked HSC past exam questions on confirming scientific findings.
- Evaluate the validity, reliability and accuracy of scientific evidence presented in claims, considering the hierarchy of evidence in medical research
A focused answer to the HSC Investigating Science Module 7 dot point on evaluating evidence. Covers the hierarchy of evidence, what each level contributes, how to identify weak claims, and worked HSC past exam questions on medical and scientific reporting.