✅ Strengths
They are free and easy to find. They cover very large numbers of people, so they are more likely to be representative. They are collected year after year, so a sociologist can spot trends over time.
Data and Evidence » Secondary Evidence: Statistics, Documents, Digital and Media Sources
What you'll learn this session
Study time: 30 minutes
Cambridge spec: 1.2.2
- Four types of secondary evidence and examples of each
- The strengths of official statistics, documents, digital sources and media content
- The limitations of each type
- How to choose the right source for a research question
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Unlock This CourseEvidence that is already out there
Last lesson you learned that secondary data is information collected by someone else. Sociologists use it all the time, because a huge amount of it is already waiting to be used. For Cambridge IGCSE, you need to know four types of secondary evidence, with examples, strengths and limitations of each.
Key terms:
- Official statistics: numerical information collected and published by governments and their agencies.
- Documents: written records. Historical documents come from the past. Personal documents are written by individuals about their own lives.
- Digital sources: information that is published online, such as websites, blogs and social media posts.
- Media content: what is produced by the mass media, such as news, TV programmes and advertising.
Official statistics
A census is official statistics: a count of everyone living in a country, usually every ten years
Governments collect figures on the whole population. Good examples are a census (a count of everyone living in a country, usually every ten years), figures on births, deaths, marriages and divorces, unemployment figures, and school exam results.
❌ Limitations
The government decides what is counted and how, so the figures may not fit the sociologist's question. They give numbers but not reasons: they show what is happening, not why. Governments may also present figures in a way that makes them look good.
Historical and personal documents
Old letters and diaries are personal documents - they show what one person really thought and felt
Documents are written records. Examples are diaries, letters, official reports and records kept by organisations. A historical document is the only way to study a society that no longer exists. A personal document, such as a diary or letter, shows what one person really thought and felt.
✅ Strengths
They give rich, qualitative detail and the writer's own meanings, so they are high in validity. They let sociologists study the past and private lives that could not be watched directly. Nobody is bothered by a researcher, so there is no interviewer effect.
❌ Limitations
The writer may be biased, or may not have told the truth. The document may be fake or hard to prove genuine. Only some people wrote things down, and only some documents survive, so they may not be representative. Old documents can also be hard to understand without knowing the time they were written in.
Official reports, such as a government report on housing or a company report, are documents too. They are written for a purpose, so a sociologist has to ask who wrote them and why.
Digital sources
Digital sources are a newer type of evidence. Examples are websites, blogs, online forums and social media posts. Sociologists can use them to see what people say, and how they describe themselves, in their own words.
✅ Strengths
They are quick, cheap and easy to reach, and there is a huge amount of them. They show people's views as they happen, in their own words. They can reach groups who are hard to meet face to face.
❌ Limitations
Anyone can post anything, so it can be false, and it is often hard to tell who wrote it. Not everyone uses the internet, and people choose what to post, so it is not representative. Posts can be deleted or changed. There are also ethical questions about using people's posts without asking.
Media content
Media content is what newspapers, news websites, TV, radio and advertising produce. A sociologist might study it to find out which groups of people are shown, and how, or what values a society holds at a certain time.
✅ Strengths
It is easy to get and often free. It shows the attitudes and values of a society at the time. The same content can be compared over many years to show how ideas change.
❌ Limitations
Owners, editors and advertisers decide what is shown, so it may be biased. Stories are chosen and shaped to be exciting, so they can exaggerate. Media content shows what is produced, not what audiences think of it.
Choosing the right source
No source is perfect. The best choice depends on the research question. A researcher asking "how has the number of marriages changed?" would use official statistics. A researcher asking "how did people feel about moving to a city a century ago?" would look for letters and diaries. A researcher asking "how are teenagers shown on TV?" would study media content.
Remember that every source needs a question: who made this, why, and how far can I trust it? This is how sociologists check bias and validity.
Common mistakes
Do not say that official statistics are "always true". They cover many people, but governments choose what to count. A diary is secondary evidence for a researcher who reads it, because someone else wrote it. Always give a strength and a limitation that match the source you were asked about, not a general point about secondary data.
Exam-style question
Source A: A researcher wanted to find out how family life has changed in one country over the last hundred years. They used the national census, letters written by families in the 1920s, and recent blog posts by parents.
(a) Identify two types of secondary evidence used in Source A. [2 marks]
(b) Explain one strength and one limitation of using personal documents such as letters. [4 marks]
Model answer
(a) The national census, which is official statistics (1). Letters written by families, which are personal documents (1). [Blog posts, a digital source, would also be correct.]
(b) One strength is that letters show what people really thought and felt in their own words, so they give detailed, valid information (1) that a researcher could not get by watching families from a hundred years ago (1). One limitation is that the writer may have been biased or may have left things out (1), so a sociologist cannot be sure the letters are true or represent all families, because only some people wrote and kept letters (1).
Exam tip
For "one strength and one limitation", write two separate points and give each a reason. Name the source type (personal documents) in your answer, and use "because" to earn the second mark of each point.