Lesson 26 — Activity 1: Reading Graphs

Getting Ready

Graphs are visual representations or pictures of data. They help us to compare data, draw conclusions, make predictions, and see trends.

They are often used in the workplace. You may see graphs that show sales of products, attendance of employees, or the types of customers that buy products.

Here's an example of a bar graph showing sales during the summer months.
Image courtesy of www.imagesgoogle.com

In this activity, you will learn about two types of graphs: bar graphs and pictographs.

A bar graph or pictograph will start with gathering information.

Below is a tally of favourite pets in a Grade 9 classroom:

Dogs — 10
Cats  —    5
Hamsters — 4
Fish — 4
Snakes — 2

A bar graph is a graph in which bars of different lengths are used to represent the information. Bar graphs are used to compare information or data that does not change. They give a snapshot of information in one period of time. The bar graph below represents the favourite pets from the tally above.

At a glance you can see that dogs are the most popular pet.

To read a bar graph, do the following:

  • read the title to see what the graph is about
  • look at the x-axis (↔) to see what is identified
  • look at the y-axis (↨) to see the numbering system used
  • read the first bar and follow it to the top to see what number is represented
  • repeat the above step for each bar in the graph

If you have a graph on a piece of paper (as compared to a computer screen), it is a good idea to use a ruler to line up the top of the bar with the scale.

Looking at this graph, you can tell that 10 students like dogs while only 2 like snakes. How many like cats? Five students list cats as their favourite pet.

Another type of graph that you may encounter is a pictograph. A pictograph is a graph in which symbols are used to represent numbers instead of bars. The pictograph below represents different ways to get to university every day.

At a glance you can see that walking is the way most students get to university.

Notice that it looks very similar to a bar graph, but instead of simply having bars, each bar has a symbol to represent exactly what the data means.

A pictograph may also use multiple copies of a picture to show the information. Each picture will represent a certain amount of data.

Here is another example of a pictograph.

Notice that each picture represents five students. Take a look at the Car row. Notice that the pictures do not have to be complete. Since there are only 13 students using a car to get to school, you cannot draw three complete cars because the drawing stops at marker 13.

Go to the next page to try a Self-check Activity on reading graphs.