Let’s continue to build our understanding of data by turning our attention now to another common type of chart: line graphs.

What’s a line chart?

A line chart is a graph or chart where data is depicted in the form of points that are connected with a line. The line forms a visual cue that helps people to better understand the peaks and troughs or the increases and decreases more easily.

While bar charts show discrete values for a certain category, line charts tend to show trends of the same data over time.

Watch the video for a full discussion about line charts.

Line charts most commonly look like this:

Source: Data.gov.au is licensed with CC BY 4.0.

But they can also vary and look like this:

Source: Data.gov.au is licensed with CC BY 4.0.

What’s the major difference between the two charts? One plots 1 series of data, while the second plots a 3 series, thereby allowing you to compare them in the same chart.

Like other charts, line charts have:

• A title.
• Units.
• Axes – some can also have an additional right-side y-axis.

But in particular, line charts are characterised by:

• plotted data points connected by lines that then show,
• trends (increases, decreases).

What insights can you see in the two line charts above? Watch the video for a full discussion.

How to answer questions relating to line charts

Interpreting data is very much based on the individual graph at hand. But there are general rules that you can follow:

1. Know the requirement.
2. Orientate yourself with the background – e.g., title, units, axes, legend/key.
3. Line charts tend to show the connection between one data point and the next to show a ‘progression’ (usually through time). Look at how the line moves, usually increases are an upward slope while decreases are a downward slope. Constants are shown as a straight line. Be aware also that a decrease isn’t always a bad thing and it is contextual – e.g., a decrease (downward slope) in a personal best running time for a 400-metre run is a positive outcome!
4. Make inferences were appropriate.

Let’s see it in action now with a worked example.

Example Question/s

Watch video for explanation of the following question/s:

Kombucha is a drink that The Live Welloy Company sells. The following sales data shows the units sold only. Income is price multiplied by units sold. Which of the following statements is correct given the data below?

Modified from source: Data.gov.au is licensed with CC BY 4.0.

A. The Live Welloy Company generated over $500 million each year from the sales of the two types of kombucha.
B. From 2007-09, “Kombu Revolu” has always outperformed “Trader Paul’s” by bringing in more money.
C. The trend of sales of units of “Trader Paul’s” through the years is inverse to that of “Kombu Revolu”.
D. The gap between sales of units sold between “Trader Paul’s” and “Kombu Revolu” is the greatest in 2016-17.

Key Rules to remember

• Use the general rules in working with data – requirement, orientate, ‘zoom in’.
• Line charts are made of data points that connected together show ‘visual’ cues (increases/decreases) so that trends can be identified more easily.
• Upward slope (increase); downward slope (decrease); straight horizontal line (constant); and straight vertical line (sharp drop or spike). Please note decrease does not necessarily mean unfavourable.
• Look for trends over a period.

Practice time!

Now, it's your turn to practice.

Here’s a thought experiment #14.

Remember, there is no formal answer and this experiment is provided to help stimulate your creativity and critical thinking (a ‘thought experiment’ is provided at the end of every checkpoint except checkpoint 18).

Thought experiment 14:

Is the world a better place for people now or was the world a better place for people in the past? Or is there no difference?

Take your time to work through this thought experiment as it is not assessed and provided to help develop your deeper thinking skills. Think about various components of the question. What questions will you ask yourself and how do you answer your questions?

Now, let’s turn to the checkpoint questions.

Click on the button below and start your practice questions. We recommend doing untimed mode first, and then, when you're ready, do timed mode.

Every question has two solutions videos after you complete the question. The first is a quick 60 second video that shows you how our expert answers the question quickly. The second video is a more in-depth 5-steps or less explainer video that shows you the steps to take to answer the question. It's really important that you review the second video because that's where you'll learn additional tips and tricks.

Once you're done with the practice questions, move on to the next checkpoint.

Now, let’s get started on your practice questions.

---