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Sampling vs Census: Differences and When to Use
Sampling vs census: how a full count differs from a sample in sampling error, cost, time and benchmark use, and when to choose each. Sourced to ABS.
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How do Census, Sampling compare side by side?
The table below compares Census, Sampling across 10 procurement-relevant dimensions, from definition through source.
Side-by-side comparison
| Dimension | Census | Sampling |
|---|---|---|
| Definition | A study of every unit, everyone or everything, in a population (a complete enumeration, or complete count). | A subset of units selected to represent all units in the population of interest; a partial enumeration. |
| What the results are | A true measure of the population, with no sampling error. | Estimates of the population's characteristics, made from the sampled units. |
| Sampling error | None. | Present, because inferences about the whole population come from a subset. For a non-random sample the sampling error cannot be estimated. |
| Cost | Higher, in both staff and money. | Generally lower than a census. |
| Time | Generally takes longer to collect, process and release; enumerating every unit within the available time may be difficult. | Results may be available in less time. |
| Benchmark data | Can provide benchmark data for future studies. | Often not suitable for producing benchmark data. |
| Representativeness | Covers the whole population by definition. | May not represent the population, particularly when the sample is small; a sample must be robustly designed and large enough to be reliable. |
| Real example from one agency | The U.S. decennial census: a count of the people living in the United States every 10 years, on Census Day, April 1, in years ending in zero. | The American Community Survey: an ongoing survey that provides information on a yearly basis. |
| Pick it when | You need a complete count or a benchmark and can afford the cost and the wait. | Cost and timing matter more than a complete count, and you can design a robust sample. |
| Source | Australian Bureau of Statistics, "Census and sample" (abs.gov.au, read 2026-10-29); U.S. Census Bureau, Decennial Census, census.gov/programs-surveys/decennial-census/about.html (read 2026-10-29). | Australian Bureau of Statistics, "Census and sample" (abs.gov.au, read 2026-10-29); U.S. Census Bureau, American Community Survey, census.gov/programs-surveys/acs/about.html (read 2026-10-29). |
Common questions
Common questions about Census vs Sampling
What is the difference between sampling and census?
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A census studies every unit in a population, while sampling studies a subset chosen to represent the population and uses it to estimate the population's characteristics. A census has no sampling error but costs more and takes longer; a sample costs less and can be faster but carries sampling error (Australian Bureau of Statistics).
Does a census have any error?
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A census has no sampling error, because it covers every unit rather than a subset. Sampling error is the error that comes from inferring about a whole population from a subset (Australian Bureau of Statistics).
Why would an agency that runs a census also run a survey?
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The U.S. Census Bureau runs the decennial census every 10 years and the American Community Survey as an ongoing survey that provides information on a yearly basis, so the two serve different timing needs.
Can a non-random sample give population estimates?
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Not reliably. For a non-random sample the sampling error cannot be estimated, which makes it difficult to infer population estimates from the sample (Australian Bureau of Statistics).
Going deeper
