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Data and Evidence » Primary, Secondary, Qualitative and Quantitative Data

What you'll learn this session

Study time: 30 minutes

Cambridge spec: 1.2.1

The difference between primary and secondary data
The difference between qualitative and quantitative data
The strengths and limitations of each type
How the two pairs combine in real research

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Where does the evidence come from?

Every piece of research needs evidence. Sociologists call this data. Before you choose a research method, you have to ask two questions. First, who collected the data? Second, what form is it in, numbers or words? The answers give us two pairs of data types, and you need to know all four.

Key terms:

Primary data: new information collected first-hand by the researcher for their own study.
Secondary data: information that was collected by someone else, for another purpose, and is used again by the researcher.

As a reminder from earlier lessons, quantitative data is information in numbers, and qualitative data is information in words that shows people's meanings.

Primary or secondary: what is the difference?

Handing out her own questionnaire means this researcher is collecting fresh primary data

🎯 Primary data

The researcher goes out and collects it themselves, for example by handing out a questionnaire, holding an interview or watching a group. It is "fresh" and made to fit the research question.

📚 Secondary data

The researcher uses information that already exists, for example government reports, old newspapers, or a table of figures from an earlier study. They did not collect it, so they cannot control what it contains.

Strengths and limitations of primary data

Strength: it is up to date and made to answer exactly the question the researcher wants to ask.
Strength: the researcher knows how it was collected, so they can judge how far to trust it.
Limitation: it takes a lot of time and money to collect, especially from large numbers of people.
Limitation: researcher effects, such as bias or the interviewer effect, can reduce its validity.

Strengths and limitations of secondary data

Strength: it is quick, cheap and easy to get, and often covers a huge number of people.
Strength: it can show change over a long period of time, and no respondents have to be bothered.
Limitation: it may be out of date, or collected for a different purpose, so it may not answer the researcher's question.
Limitation: the researcher does not know how well it was collected, or whether its author was biased.

Qualitative or quantitative: what is the difference?

Counting heads gives quantitative data; asking why they chose that answer gives qualitative data

🔢 Quantitative data

Numbers, percentages and statistics. For example, "62% of students walk to school". It is easy to count, compare and show in charts.

💬 Qualitative data

Words, descriptions and opinions. For example, "I walk because my friends do and we talk the whole way". It explains feelings, reasons and meanings.

Strengths and limitations of quantitative data

Strength: it is easy to compare, and patterns and trends can be spotted quickly.
Strength: studies using it are easy to repeat, so it is high in reliability, and it can cover a large sample.
Limitation: it tells us what is happening but not why. It has less detail, so it is lower in validity.
Limitation: the researcher decides the categories, so people may not be able to give the answer they really want to give.

Strengths and limitations of qualitative data

Strength: it is rich and detailed, so it gives a valid picture of people's own views.
Strength: it can show unexpected ideas that the researcher had not thought of.
Limitation: it is hard to compare and takes a long time to collect and write up, so samples are often small.
Limitation: it is harder to repeat, so it is lower in reliability, and the researcher's own views may shape how it is read.

Putting the two pairs together

The two pairs are not rivals. They answer different questions: who collected it? and what form is it in? So every piece of data is one from each pair. That gives four combinations.

📝 Primary quantitative

Results from a questionnaire that the researcher handed out, using closed questions that give numbers.

🎤 Primary qualitative

Quotes from interviews that the researcher carried out, or notes from a group they watched.

📊 Secondary quantitative

A table of figures that a government or another researcher published.

📰 Secondary qualitative

Written accounts by other people, such as an earlier researcher's interview notes, read by the researcher for ideas and meanings.

The positivist approach tends to prefer quantitative data, and the interpretivist approach tends to prefer qualitative data. Many researchers use both, which links to triangulation from the earlier lesson on mixing methods.

Worked example

A researcher wants to know why students in a city are late for school. She hands out a questionnaire to 200 students and finds that 35% say they are late at least once a week. This is primary quantitative data. She then looks at a table of attendance figures that a local council has already published. This is secondary quantitative data. Finally she interviews 8 students to ask them why. This is primary qualitative data. Together they tell her how many students are late, how this compares with the whole city, and why it happens.

Common mistakes

Students often say that primary data is "better" than secondary data, or the other way round. Neither is always better: it depends on the research question. Another mistake is thinking that all secondary data is quantitative. An earlier researcher's interview notes are secondary and qualitative. Finally, always say why something is a strength: "it is cheap" is only half an answer without "so a large sample can be reached".

Exam-style question

Source A: A researcher wants to find out how much homework students do in one town. She gives a questionnaire to 300 students in four schools, with questions such as "How many hours of homework do you do each night?" She also reads a report on homework that was written ten years ago by the local council.

(a) From Source A, identify two types of data that the researcher used. [2 marks]

(b) Explain one strength and one limitation of using primary quantitative data. [4 marks]

Model answer

(a) Any two: primary data from the questionnaire (1). Quantitative data, as the answers are in hours (1). Secondary data from the council report (1).

(b) Strength: the questionnaire gives numbers, so the results can be easily compared and shown in charts (1), which makes it quick to spot patterns in how much homework students do (1). Limitation: the questionnaire tells her how many hours students do but not why (1), so the data lacks detail and may be lower in validity (1).

Exam tip

In part (b), label your answer "Strength" and then "Limitation" so the examiner can see both. Give a reason for each one, and use details from Source A, such as the hours or the 300 students.

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