Grouped data – What it is, definition and concept

The grouped data are those that are classified according to a criterion, showing a frequency for each class or group formed.

That is, the grouped data is separated by categories, and each data or observation can only belong to one category (not two or more):

We must remember that a statistical data is the representation of a qualitative or quantitative variable. This, by assigning a number, letter or symbol.

Another important issue to mention is that, according to the sources reviewed, grouped data is usually used when it comes to samples of more than 20 data. On the other hand, with smaller samples, it is not so necessary to group.

The fundamental objective of grouping the data is that their analysis can be easier, so that a first approximation of the results can be made quickly.

In addition, the grouping serves to be able to elaborate, from the collected information, visual tools such as a histogram, a bar graph or a pie chart.

Difference between grouped and non-grouped data

The main difference between grouped and non-grouped data is that the former have been divided by categories, as we have mentioned. On the other hand, the non-grouped data is presented as it has been collected, without any modification (perhaps they can be ordered, for example, from smallest to largest).

As we had previously pointed out, the size of the sample is a factor to take into account. If we had a thousand data, for example, the most practical thing would be to summarize the information in a table where the frequency distribution is observed.

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We must remember that the frequency distribution is the way in which a set of data is classified into different mutually exclusive groups. That is, if a piece of data belongs to one group, it cannot be part of another.

Grouped data example

An example of grouped data would be the following, where we have summarized the information on the monthly income of a group of people:

Monthly income Frequency
[1.500-2.500] 120
(2,500-3,500] 210
(3,500-4,500] 300
(4,500-5,500] 250
(5,500-6,500] 400
(6,500-7,500] 510
(7,500-8,500] 420
(8,500-9,500] 416
(9,500-10,500] 100

In the table we can see that, for example, 210 people in the sample have a monthly income of between 2,500 and 3,500 euros.

Now, if the data were not grouped it would simply be displayed as a list:

Name Income
Samuel Sanchez 2,700
Alex Benavides 3,100
Ernesto Jimenez 4,500
Alicia fernandez 6,100
Beatriz Borja 2,900
Vilma Zapata 3,400

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