Collecting Data
Collecting data covers the practical methods used to gather information for a statistical investigation, including surveys and questionnaires, observation, experiments, and using data that already exists (secondary data). The method chosen depends on the type of data needed, the population being studied, and practical factors like time and cost. GCSE Statistics exams often ask you to identify a suitable method or to critique a data collection method used in a given scenario.
Method
- Decide what data you need (its type, and whether primary or secondary data is appropriate) before choosing a method.
- For primary data, choose between a questionnaire/survey (asking people directly), an experiment (controlling variables to test something), or observation (recording what happens without intervening).
- For secondary data, identify a reliable existing source, such as government statistics or published research, and check it is relevant and up to date.
- Consider practical factors: cost, time available, and how easy the data is to access, since these can limit which method is realistic.
- Check the method for possible sources of bias, such as leading questions, a non-random sample, or observer effects.
- Pilot the method on a small group first if possible, to catch problems before collecting the full data set.
Worked example
A student is investigating whether it rains more in the north of the UK than the south. Suggest a suitable method of collecting the data she needs, and explain your choice.
- Identify the data needed: rainfall amounts (in mm) for locations in the north and south of the UK over the same time period.
- Consider primary data collection: setting up rain gauges herself in several towns would take a long time and be hard to do accurately across a whole country.
- Consider secondary data: the Met Office already publishes reliable rainfall records for towns across the UK.
- Choose secondary data, since it is already collected accurately over a long period and covers far more locations than she could measure herself.
- Final answer: use secondary data (existing published rainfall records), because it is more reliable, wide-reaching and practical than collecting primary data herself.
Practice questions
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Exam-style questions
Written in the style of a GCSE Statistics exam paper, with a full mark scheme.
A researcher wants to find out how long people spend commuting to work. State one primary method she could use to collect this data, and one advantage of that method.
A gym wants to know how satisfied its members are. It leaves a box of comment cards at the reception desk. (a) State one problem with this method of data collection. (b) Suggest a better method. (c) Give one reason your suggested method is better.
A scientist wants to test whether a new fertiliser increases the height of tomato plants. (a) State the type of data collection method most suitable (survey, observation, or experiment). (b) Explain your choice. (c) State one variable she should keep the same between the group given fertiliser and the group not given fertiliser.
Free printable worksheet
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