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Good Graphs

Good graphs are effective tools. Adrian Gepp talks about features of good graphs here.
Now there are different types of graphs, but overall what good graphs ,how do we produce good graphs? What are the things that we need to keep in mind? Again it’s an art form, it’s not an exact science. But good graphs are always clear and well labeled. Think about do I have titles on my graph, do I have access titles on my graph, do I need to have those additional labels like on top of the bars, like those data point labels? Maybe, maybe not but think about that good graphs are concise and informative. Think about why are you doing the graph? What is the purpose of the graph?
And based on that try and focus the reader on the substance, what you want them to extract from it, not the form, not the pretty colour or the whatever it is. Now we use colour we use nice pictures we use all of that to help make it more attractive, but fundamentally it’s about the substance. What is the information you’re trying to convey? Then we use nice colours and help it out, but it’s not just all about fancy nice colours that look good but don’t display the information, that’s not okay. So step one, we want to be concise informative focus on the substance, then we make it look pretty.
Now generally good graphs encourage comparisons between categories, trends over time, usually that’s what we’re we’re looking at, because visually our eyes are very good at picking comparisons, and finally good graph should be accurate. They should not be misleading, we should use accurate figure,s and when we talk about ethics we’ll talk a little bit more about that. So, graphical techniques, there’s a saying in English that a picture is worth a thousand words and that’s very true here. So we’re trying to summarise a lot of information, it would have taken tables and lots and lots of text to convey this, but we show one graph and the reader can quickly see all that information.
Now as managers you’re time poor, so this is really helpful to you to find out that information quickly and efficiently, to communicate it with your team, with your bosses, with other managers. So really think about when you’re writing reports whatever you’re doing, is there a graph here? When you’re presenting data, is there a graph that might be a nice way to present this? That will quickly and easily communicate this information. When you’re asking people to prepare and do some data analysis for you, yeah tell them to think about hey I would like to see these results in a graph, because that’s easier for me to quickly see it.
Then give me all the other information and the backup information, but a nice summary graph can do a lot of good. But we need to use the right graph, so we’ve seen bar and pie charts, really good when we can break things down into categories, and either focus on the contribution to the whole or comparing the different categories. We looked at histogram for quantitative variables, numerical variables, the numbers, breaking them into categories then we can look at frequencies of relative frequencies. We looked at line plots for a time series graph so we could see what was happening over time. Finally, we looked at a scatter plot to see the relationship between two graphs.
But now it’s time to actually do this in Excel so now that we’ve seen these, let’s have a play in Excel to make sure we can calculate them and produce them in Excel. Good news is very easy so not too difficult but there’s lots of different options so you need to spend some time in playing around to see what’s happening.

What makes a good graph?

It’s easy to spot a bad graph.

I’m sure everyone has seen graphs before that only made the data more confusing. A quick search will turn up many. Sometimes they are simply hard to decipher, due to a bad choice of graphical technique or because of poor labelling. Other times, they may be misleading and result in incorrect interpretation of the data. To effectively communicate our results, we need to focus on making good graphs.

Constructing a good graph can be a bit of an art form, but there are some basic principles. Applying these principles puts us on the path to a final graph that is effective in communicating important facts about the data without being misleading. In the above video, Adrian outlines some of these principles. While we adhere to these principles in this course, others might not by accident or to be deliberately misleading. When we talk about the role of ethics in analysis (Activity five) we’ll show some examples of really bad graphs.

You’ve now finished with this first activity! Hopefully you have a greater appreciation for different types of visualisations, when they should be applied, and what we need to consider to make a ‘good’ graph. You now have the opportunity to check your understanding with a quick quiz.

From there, we’ll step through these same graphical techniques and examples to demonstrate how you can also construct them using Excel.

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Data Analytics for Decision Making: An Introduction to Using Excel

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