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A census is a method that collects information from the entire population targeted by a study.
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A survey is a method that collects information from a part of the population targeted by a study, called a sample.
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An inventory is a method that collects information concerning objects rather than living beings.
To clearly differentiate between these basic statistical concepts, here are some examples.
Examples of a census
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Ask all the students in the school what they think about the food in the cafeteria.
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Ask all residents of a municipality about their intention to vote in the next municipal election.
Examples of a survey
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In a school, only one class per grade is asked to rate the quality of the food in the cafeteria.
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In a municipality, only customers at a general store are asked about their intention to vote in the next municipal election.
Example of an inventory
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In order to know how many boxes of nails to order for the next delivery, the employees of a hardware store count all those already available in the store.
It is important to identify the type of variable needed to collect data for a research question.
For example, if we want to know the favourite colour of a population, the answers to the questionnaire will be words such as red, green, blue, etc. However, if we are interested in the number of children in each family, the answers to the questionnaire will be natural numbers such as |0,| |1,| |2,| etc.