What is a Census: Overview
A census is where every member of a population is studied. It results in a parameter for a population, as opposed to a statistic (How to tell the difference between a statistic and a parameter). Studying every member of a population is usually impractical because of financial of time constraints. With the exception of the U.S. Census, censuses are very rare.
What is a Census: Sampling
A census is a way to obtain and record information about every member of a population. It’s a term mostly connected with national information although the term can be used with smaller populations. A census is the opposite of sampling: with a census, every member of the population is included in the results and with sampling, only a small percentage of the population is included. Therefore, censuses tend to be more accurate than sampling although with a well-conducted survey using sampling, it is possible to get a fairly accurate picture of the entire population. Because of the possibility of error in sampling, confidence intervals are usually associated with sampling. For example, a national poll might give results as having a 98% confidence interval.
The U.S. Census
The U.S. Census is conducted every ten years, for years ending in 0. For example, a census was held in 1990 and another in 2000. Historically, polling staff have contacted individual households via mail and direct contact. However, it is expected that many households will be able to fill out census information using the internet. Participation in the census is mandatory. Refusing to participate in the census can result in hefty fines.
The Economic Census is conducted every five years, for years ending in 2 an 7. For example, there was a U.S. Government Economic Census in 2007 and 2012. The Economic Census provides information about American businesses.