A picture can make a complex idea simple and easy to understand. This is why it is very useful in the representation of data.

In this article, we will learn about different charts and diagrams that are used to present data in a simple form.

## Charts and diagrams meaning

Charts and diagrams are a visual representation of mathematical concepts and data.

Charts and diagrams are for illustration purposes. They give a clearer understanding of a concept or some information that needs to be passed. They are made up of symbols, shapes, and notations that make it easy for one to navigate and interpret the data that is being presented.

Charts and diagrams are in the form of graphs, tables, and figures. As we continue, we will get to know about examples of charts and diagrams and what they look like.

## Charts and diagrams in statistics

Statistics involves the collection of data from multiple quantities for the purpose of analysis and finding information. The data that is being collected can be represented with charts and diagrams.

From the charts and diagrams, you will be able to make an analysis and possibly predict future outcomes.

Let's take a look at some of the charts and diagrams used in statistics.

## Types of statistical charts and diagrams and their uses

### Bar chart

Bar charts are used to compare data. The data is organized in categories in form of rectangular bars on a graph and from there you can compare different categories of data.

The rectangular bars are usually of different heights and they can be represented horizontally or vertically.

For example, the bar chart below shows information gathered from a group of students on which sports they like the most.

From the graph, you can tell which sport is most liked or least liked and you can also tell the number of students who like the sports. The most liked sport is football with 8 students liking it and the least liked sport is cricket with just 1 student liking it.

Below is a horizontal representation of the bar chart.

**Uses of bar charts**

- A bar chart is used to visually display and analyze data.
- It is used to compare data in categories.
- It is used for illustration purposes.

### Pie chart

This chart is called a pie chart because it is circular and it is sectioned in a way that it looks like slices of a pie. The pie chart represents data that is split into different categories. The categories are the slices of the pie.

For example, if you want to categorize the percentages of a population that like different kinds of fast-food restaurants, we can do that in a pie chart.

In the pie chart above, we can see what percentage of the population like the various types of fast-food restaurants. The size of the slice or part of the pie chart that represents a category should correspond to the proportion or value of the data. Using the pie chart above as an example, this means that the section representing 20% can't be used to represent 50% because of the size.

**Uses of Pie chart**

- A pie chart is used to split complex data into smaller and simpler categories.
- It is used to show the proportion of categories of data.

### Histogram

Just like the bar chart, the data in a histogram chart is represented with bars but a histogram organizes data in ranges. It shows the frequency at which different ranges of data occur.

For example, you can categorize the ages of people in a congregation to know how many people are of a certain age.

From the histogram above, you can tell the number of people in the congregation according to their age range.

Now, take a look at the histogram and the bar chart. Did you notice any difference in the way they are presented? The bars in the bar chart and spaced but for the histogram, they are placed together, with no space between them.

**Uses of a histogram**

- Display data in categories and ranges.
- Find the frequency of an event.
- Organize and summarize a large set of data.

### Line chart

A line chart is also called, a line plot or line graph. It is used to show how variables and information change over time. The information on a line chart is represented with points and the points are connected with a continuous line.

For example, if you have information on how the price of petrol changed over 5 months, you can represent that in a line chart so that the trend can be viewed and studied.

From the figure above, we can study the trend and see how the price of petrol moved up and down over the months.

**Uses of a Line chart**

- See how data changes over time.
- Track the trend of an occurrence.
- Show and compare change over time.

### Venn Diagram

A Venn diagram is a diagram that aims to show the relationship between groups or quantities. The groups to be represented are called sets. It is made up of overlapping circles and the number of circles depends on how many quantities you want to represent.

Consider two sets of people. One set likes oranges and the other likes apples.

$Oranges=\{John,Sarah,Morgan,Dan,Dylan,Tami\}\phantom{\rule{0ex}{0ex}}Apples=\{Tom,Chris,Lindsey,Dan,Tami,Mary\}$If you were to draw a Venn diagram to represent this, it will look like the diagram below.

From the diagram, you can see the two circles representing the fruits and the names of the people who like the fruits in the circles. Notice that there are two names in the part where the circles overlap. That part is called the intersection and it means that Dan and Tami like both oranges and apples. The rest of the people like either orange or apple.

#### Uses of the Venn diagram

- Show the relationship between sets for comparison.
- Represent and analyze data.
- Predict and compare possible events in Probability.

### Scatter Plot

A scatter plot displays the relationship between two sets of data. In a scatter plot, dots are used to represent the values of the data. After collecting data and plotting it, the pattern of the dots on the plots will tell the relationship between the sets that are being compared.

For example, if you have information about a person's weight at different ages of his life, you can represent that in a scatter plot and it will look like the figure below.

From the pattern in the scatter plot above, we can see some fluctuations in his weight over the years and you can also see that his weight reduces as he gets older.

**Uses of a scatter plot**

- It is used to show the relationship between two sets of data.
- It can be used to observe relationships and see how data interact.

### Flow chart

A flow chart is a process diagram. It shows the steps to follow for a particular process and also makes the steps easier to follow. If the procedure is a complex one, it can be made simpler with a flowchart.

The steps are written in different shapes and they are connected with lines that indicate what step to take next. Any process can be visualized clearly on a flowchart and if followed carefully, there will be no mistakes. Below is an example of a flowchart.

The flow chart above shows the process of getting an even number when a dice is rolled. If an even number is obtained after rolling the dice, the process ends. Otherwise, you roll the dice again. The chart shows the complete process. It shows what to do and the decisions that can be made.

**Uses of a flow chart**

- Show the process of a system.
- Study the process of a system.
- Document the process of a system.
- Communicate clearly how a system works.

## Difference between data flow diagram and flowchart

A data flow diagram (DFD) is a diagram that shows the flow of data of a system or process. Just like a flowchart, DFD also makes use of shapes to show the flow of information.

The data flow diagram above is for a food ordering system. It only shows the flow of data for the process but doesn't give detailed information on how the food will be ordered, how the food gets to the kitchen, and what decisions were made.

It is easy to think that a DFD is the same as a flowchart but there's a lot of difference between both. The table below shows the difference between a DFD and a flowchart.

Data Flow Diagram | Flowchart |

It shows just the flow of data in a system. It does show the steps or decisions made. | It gives detailed information about the step-by-step process. |

It shows only the functionality of a system. | It shows how to make the system function the way it should. |

It gives a high-level view of a system. | It gives a low-level view of a system. |

It does not show the order in which procedures or steps should be taken. | It shows the order in which procedures or steps should be taken. |

It only explains the actions to be taken and not how the system will work. | It explains the actions and how the system will work. |

## Interpreting charts and diagrams

The purpose of representing data in charts and diagrams is to enable one to see and understand the data that is being presented. Having that in mind, interpretation won't be too difficult if you pay attention to details.

Charts like a bar chart, histogram, line charts and scatter plots, where the data is represented on a Cartesian plane, usually have legends on the sides of the x and y-axis that tells us what the chart represents. The legend can give information on the unit of measurement and what is being measured.

The legend of a graph tells what the graph represents.

We can also tell what the charts and diagrams are talking about by looking at the title. Everything is visible so we would find other information written on the graph.

Like in a pie chart and a Venn diagram, the group or sets that are involved are written alongside their values. If any symbol is used, you will see it on the diagram.

It can sometimes be overwhelming to interpret plots, especially in the case of a scatter plot. But all we have to do is follow the pattern of the points on the plot and then we will be able to interpret and know what's going on.

## Charts and diagrams - Key takeaways

- Charts and diagrams are a visual representation of mathematical concepts and data.
- Charts and diagrams are for illustration purposes. They give a clearer understanding of a concept or some information that needs to be passed.
- The bars in the bar chart and spaced but for the histogram, they are placed together; no space between them.
A bar chart can be represented either vertically or horizontally.

Be careful not to mistake a data flow diagram for a flow chart. They are similar but have a lot of differences.

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##### Frequently Asked Questions about Charts and Diagrams

What are chart and diagram?

Charts and diagrams are a visual representation of mathematical concepts and data.

What are a diagram and its types in statistics?

A diagram is a visual representation of a concept or an idea. Types of diagrams in statistics include:

- Bar chart
- Histogram
- Pie chart
- Scatter plot
- Venn Diagram
- Data flow diagram

What are the types of charts?

Types of charts include:

- Bar chart
- Pie chart
- Histogram
- Flow chart
- Venn Diagram

What is diagram interpretation?

Diagram interpretation is reading and understanding the data that is being presented on a diagram.

What is the purpose of charts and diagrams?

Charts and diagrams are for illustration purposes. They give a clearer understanding of a concept or some information that needs to be passed.

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