Effect of sample size on sampling error

The larger the sample size, the smaller the sampling error. However when the population is large, sampling a small proportion of the population may still give accurate estimates.

Sampling error depends much more strongly on the sample size than on the proportion of the population that is sampled.

For example, a sample of 10 from a population of 10,000 people will estimate the proportion of males almost as accurately as a sample of size 10 from a population of 100.

The cost savings from using a sample instead of a full census can be huge.