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Chart examples and the stories they tell

Charts tell the story of data that tables of data cannot.

Looking at a spreadsheet of data does not provide any meaning to a reader or an audience.

A chart, however, immediately makes clear the patterns in the data. Facebook and YouTube are the most used social media sites among students, followed by Instagram and TikTok. The above chart is a bar chart: horizontal bars tell us the number of students using that site.

Another type of chart is the pie or circle chart. In this chart YouTube is the site students spend the most time on, TikTok comes in second with six students reporting that they spend the most time on TikTok. They are 26.1% of the students surveyed. Circle charts are good for reporting percentages.

A column chart depicts data as columns. These are number of positive tests for Covid-19 in Yap state through 29 August 2022. This chart tells a story of a rising surge in Covid-19 cases on the island in August 2022.

The above column chart is for Kosrae state. The columns are the number of positive test results and the number of people treated for Covid-19. The dark yellow line is the positivity rate: the number of positive tests divided by the number of people tested. The spike on 22 August was because only one person was tested and they were positive: 1 ÷ 1 = 1 which is 100%. That is an outlier and does not have any useful meaning.  This kind of chart is also called a combination chart because it combines two kinds of charts. The story told by this chart is that the Covid-19 surge is over on Kosrae. There will still be one or two positive test results in the days, months, and years to come.

The above chart is a line chart for Covid-19 positive cases reported in the Marshall Islands. At peak RMI recorded just over 1400 positive test results in a single day. The last report charted above was around 90 positive cases nationwide. This is a line chart. A column chart for this many different data sets (four data sets: Majuro, Ebeye, neighboring islands, and RMI total) would be confusing to look at. In this case a line chart is appropriate.

Pohnpei displayed positive test results (cases), encounters (number tested), and treated using a column chart with three different colors.

There are many kinds of charts. In chapter three there was a special kind of column chart called a histogram. In chapter four we will meet xy scatter graph charts. Chapter two introduced the box and whisker plot. Charts help tell the story of data. Charts turn piles of numbers into comprehensible images, pictures, visualizations, and help us understand the data. Charts help tell the story of the data. The Covid charts above tell us that Kosrae, Pohnpei, and RMI have come through their Covid-19 surge. The Yap chart for August 2022 told us that Yap was just beginning to enter the growth stage of their surge in August 2022. 

There are college courses in data visualization - a term that includes charts and visualizations that do not look like traditional charts. Pictures tell the story of the data.