Two routes, and the difference decides how much you can trust what you end up with.
Primary
- You collect it yourself, for your question
- Surveys, interviews, sensors, observation, experiments
- Costs time and money; you control the quality
- You know exactly how it was gathered
Secondary
- Someone else collected it, for their question
- Government figures, company reports, open datasets
- Cheap and fast; you take what you are given
- You may not know who was left out of it
The question to ask of secondary data: Not “is it accurate?” but “who was it collected from, and who was missed?” Data gathered from smartphone users leaves out everyone without one.
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Collected data is useless in a heap. A database organises and structures it so that it can be found, managed and updated \u2014 which is the guide's own wording and worth learning.
What organising gives you
Findable
You can ask for exactly the records you want instead of reading everything.
Manageable
One fact lives in one place, so correcting it corrects it everywhere.
Updatable
Records can change over time without the older version being lost or duplicated.
Linkable
Separate collections can be joined \u2014 which is powerful, and is where most privacy problems start.
Classification is a choice: Deciding the categories decides what can be counted. A form with three boxes for something that has five real answers has already thrown two of them away.
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The biggest datasets are not surveys any more. They are the records a system produces while doing something else \u2014 and those records only cover the people who use the system.
Real-world examples you can name
Aadhaar, India's biometric ID system — launched 2009; Supreme Court ruling September 2018
A national identity number linked to fingerprints and iris scans, used to authenticate access to services. The Supreme Court upheld the scheme for welfare and tax purposes but struck down its use by private companies, and reporting has linked authentication failures to people being denied rations.
Who it affected: Over a billion enrolled residents, and in particular those whose fingerprints scan poorly — manual labourers and older people.
The people still offline — ITU Facts and Figures — 2023 estimate
The International Telecommunication Union estimated roughly 2.6 billion people had never used the internet, with the gap concentrated in low-income countries and, within countries, among women, rural populations and older people.
Who it affected: About a third of humanity, who cannot reach services the rest treat as default.
The gap that matters: If a city plans bus routes from app data, it plans for people with smartphones. The people most dependent on the bus may be exactly the ones the data cannot see.
How this is tested — you have to name collection methods and then say what each one misses. It comes up two ways:
Paper 1 — structured question
- Part b: explain methods of primary data collection for a task
- Part c: evaluate a decision made from one dataset
Paper 2 — source-based question
- Q2: analyse how a source gathered its evidence
- Q4: synthesise sources on whose data an organization holds
The trap: naming methods without judging them: A list of three methods is worth three marks at most. The difference between mid and top band is saying which method suits the question and who each one leaves out.
Explain two methods of primary data collection a council could use to plan a new cycle lane.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.