Question

Why are there different types of charts and graphs for different types of data (nominal, ordinal, scale?)

Why do some charts use "frequencies" and others use real numbers? What is the difference?

Answer 1

The reason for having different types of Graphs and Charts because they serve different purposes, they illustrate different different things. That is the reason we use different types of graphs.

Now, the reason why there are different graphs for different types of data because....the data types or scales are different.

Some scales are Nominal, some are ordinal, some are Ratio while some are interval. This separates or differentiates them to have different types of graphs and charts.

Before deciding which type of graph or chart we want to use, we must ask ourselves the following :-

What do I want my graphs and charts to :-

i) Compare values;

ii) Show the composition of a particular thing;

iii) Study the distribution of data;

iv) Analyse trends of the data;

v) Understand the relationships between the values in data.

According to our requirements, our charts and graphs differ.

Now, let us understand why some charts use frequencies while other use real numbers and what is the difference between them. This will also answer the earlier question of the reason behind having different Graphs and Charts for different types of data.

Consider an example, suppose we have prices of 4 different objects. On the other hand, suppose we have ages of a group of 50 people of different ages.

Now, the question comes, how to illustrate these two datasets using graphs and charts.

Notice that, in first case the data is Categorical. While, in the second case, the data is Continuous i.e. Interval.

So, if thought that, we will use the same graphical tool for both the caes, then this approach won't work.The reason being the data types are different. That's the reason behind having different types of Graphs and Charts and using them for different scales of data.

So, in first case, where the data is Categorical, we use a Bar Graph to show the comparison between all the 4 objects.

Whereas, in second case, the Bar graph cannot be used because the scale is interval scale i.e. continuous.

So, we use Histogram to show the comparison between the different age groups.

In this way, we can see that in first case the Bar Graph uses Real Numbers, while in the second case the Histogram uses the frequencies or intervals.

In order to get more comfortable with the concept of graphical tools, the reader is advised to understand the differences between various graphs, their properties and shortcomings. Studying more and more about application of graphical tools on real life data will increase the understanding as well as knowledge in this field.