Representative Sample Examples

In statistics, it is called sample to a portion of a larger and incomprehensible set, which is used to infer the nature of the whole. It is a small portion of a group of objects or people that helps us to study the whole group. A sample is representative when it has the characteristics to serve as a representation of the whole, that is, when it is a fairly faithful reflection of the complete set.

The samples, however, can never be fully representative of the entire set, that is, they can never represent it 100%. What researchers and statisticians bet on, then, is to give a sample that has the necessary characteristics to resemble the whole with a reasonable probability. To do this, attention is usually paid to the following conditions:

By guaranteeing these main conditions, a representative sample of the population whole, that is, an eloquent fraction with respect to the whole, and that serves to obtain more or less true conclusions. Otherwise, the sample taken could lead us to statements and conclusions that, when contrasted with the whole, are impossible or irrelevant.

Representative Sample Examples

The following are some examples of representative samples:

1. In a presidential election, it is very unlikely that the entire electoral roll will participate, since there are people who do not vote. In addition, many of the country's citizens do not have permission to vote, such as minors and foreign residents. However, the number of voters is so large and so significant that it can be understood as a faithful reflection of the popular will of the entire country.
2. In a survey carried out in a city, the opinion of the inhabitants is asked regarding certain road measures. If the opinion of the wealthy neighborhoods is collected only, the opinion would be positive but unreliable, since these represent barely 10% of the total population of the city. The middle class, on the other hand, constitutes 40% and the lower classes the remaining 50%. So the pollsters decide to poll 100,000 people, 10,000 of whom will be from the wealthy neighborhoods, 40,000 from the upper class. medium and 50,000 from poor neighborhoods, so that the sample is representative of the socioeconomic distribution of the inhabitants of the town.
3. A car company wants to know what percentage of the population will change cars next year. for which he establishes a random query among the clientele of a series of parking lots in the town. In order for the sample to be representative, you will need to choose the right number of parking spaces and the right number of customers surveyed, as otherwise you might take the impression that there are more people willing to change cars than there really are, for example, if you do the survey only in the capital city where the highest income.

References:

• “Statistical sample” on Wikipedia.
• “What is a representative sample?” on the Foundation for Advanced Social Research (Spain).
• "Basic concepts on inference" in the University of Valencia (Spain).
• “What is a representative sample?” on ERA Group.

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