9609 · 3.2.3
Sampling flashcards
Revision flashcards for Cambridge 9609 Sampling (syllabus 3.2.3). Flip, recall, then mark a real past-paper question.
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Why sample?
Cheaper and faster than surveying entire population; feasible for primary research.
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Random sampling?
Every member of population has equal chance of selection — reduces selection bias.
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Stratified sampling?
Population divided into strata (e.g. age groups); random sample from each in proportion.
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Quota sampling?
Interviewers fill quotas (e.g. 50 male, 50 female) to match profile — not random within quota.
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Sample bias?
Sample does not reflect population — results cannot be generalised.
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Larger sample?
Usually more reliable (lower sampling error) but higher cost.
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What is meant by the 'population' in market research?
The entire group of people from which a sample is drawn, and about whom a business wants to make conclusions (e.g., all university students in London).
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Define 'Stratified Sampling'.
A probability sampling method where the population is divided into distinct subgroups (strata) based on shared characteristics. A random sample is then taken from each stratum, often in proportion to its size in the overall population.
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What is 'Quota Sampling'?
A non-probability method where the researcher identifies subgroups in the population and sets a target number (a quota) of individuals to be sampled from each. The researcher then selects participants non-randomly until the quotas are filled.
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Explain 'Sampling Bias'.
A systematic error in the sampling process that causes the selected sample to be unrepresentative of its population. This leads to inaccurate results and flawed conclusions.
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What is the key difference between probability and non-probability sampling?
In probability sampling, every member of the population has a known, non-zero chance of being selected, typically through a random process. In non-probability sampling, selection is subjective and not based on random chance.
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What is a 'sampling frame'?
A list of all the items or people forming a population from which a sample is taken (e.g., a customer database, an electoral register, or a school's student list).
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What is convenience sampling?
A non-probability sampling method where participants are selected based on their easy availability and proximity to the researcher. It is quick and cheap but prone to significant bias.
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What is systematic sampling?
A probability sampling method where a random starting point is selected and then every 'nth' member of the population is chosen from a sampling frame. For example, picking every 100th person from a list.