Case Studies and Longitudinal Studies as Research Methods
A case study is an in-depth, detailed study of a single example, such as one person, group, school, event or community, often combining several methods, such as observation and interviews, to build a rounded, detailed picture.
Before you start
Make sure you're comfortable with these topics first:
Method
- Identify whether the question is about a case study, one example studied in depth, or a longitudinal study, the same group studied repeatedly over time, since these are different tools with different strengths.
- Link case studies to depth and validity, but weigh this against low representativeness and limited generalisability.
- Link longitudinal studies to their unique ability to show change and development over time and to establish patterns more convincingly than a single snapshot study.
- Always be ready to explain 'sample attrition' by name as the key practical weakness of longitudinal research.
- Name a real UK longitudinal study, such as the Millennium Cohort Study or the National Child Development Study, which has followed people born in 1958, if asked for an example.
- In evaluation answers, weigh the depth or insight of a case study, or the long-term trend evidence of a longitudinal study, against the cost, time and representativeness problems each creates.
Worked example
A research team begins following 1,000 babies born in the same year, planning to interview their families every few years until the children reach adulthood, to study the long-term effects of childhood poverty. After 20 years, only 620 of the original 1,000 participants remain in the study. Explain what has happened to the sample, and explain one problem this creates for the study's findings.
- Identify what has happened: the study has experienced sample attrition, participants dropping out of the longitudinal study over its 20-year run, reducing the original sample of 1,000 to 620.
- Explain the problem this creates: if the participants who dropped out share particular characteristics, for example families who moved home more often, or families in more unstable circumstances linked to poverty, the remaining 620 participants may no longer be representative of the original sample or of the wider population of children born that year.
- Conclude: this could bias the study's final conclusions about the long-term effects of childhood poverty, since the group most affected by the issue being studied may be the group most likely to have been lost from the sample.
Practice questions
Try each question, then tap to reveal the answer.
Q1What is a case study?Show answer
Answer: An in-depth, detailed study of a single example, such as one school, one community or one family, often using several research methods together.
Q2What is a longitudinal study?Show answer
Answer: A study that follows the same group of people, a panel, and collects data from them repeatedly over an extended period of time, often years or decades.
Q3Name one real longitudinal study of a UK population.Show answer
Answer: The Millennium Cohort Study, which has followed a large sample of children born in 2000 and 2001, or the National Child Development Study, following people born in 1958.
Q4What is meant by 'sample attrition'?Show answer
Answer: The gradual loss of participants from a longitudinal study over time, as people drop out, move away, or become uncontactable.
Q5Give one strength of a case study compared to a large-scale survey.Show answer
Answer: It can produce much more detailed, in-depth data about the case being studied, giving higher validity than a brief, standardised survey question.
Q6Give one weakness of a case study.Show answer
Answer: Its findings, based on just one example, usually cannot be generalised to a wider population, so it has low representativeness.
Q7Give one advantage of a longitudinal study over a one-off, cross-sectional, survey for studying how attitudes change with age.Show answer
Answer: It tracks the same individuals over time, so any changes recorded can more confidently be linked to ageing or experience, rather than simply reflecting differences between different people surveyed once.
Exam-style questions
Written in the style of a GCSE Sociology exam paper, with a full mark scheme.
Explain two limitations of longitudinal studies in sociological research.
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A sociologist conducts a detailed case study of a single, high-achieving comprehensive school to draw conclusions about what makes British state education effective. Evaluate how representative the findings from this one school are likely to be of state education across the country as a whole.
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Discuss the strengths and limitations of longitudinal studies for researching how people's lives change over time.
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See real GCSE Sociology past-paper questions, with official mark schemes →
Free printable worksheet
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