Interpreting and formatting charts

Hello students, welcome to Kwickprep. A chart is only useful if you can read it, and if it is easy to read. Can a chart mislead you? Yes, it can. Today we will learn how to interpret a chart, and how to format it so it tells the truth clearly.

This lesson has two skills. To interpret a chart means to read it and explain what the data shows. To format a chart means to change its look, like colours, fonts and labels, without changing the data. The two skills go together, because good formatting makes a chart easy to interpret.

We will read a column chart made from this canteen data. It shows tea cups and samosas sold each month. January starts at four hundred twenty cups of tea. February dips to three hundred eighty. March is the highest month. April falls to three hundred, during exams.

Follow the same five steps for any chart. First, read the title, which tells you the topic. Second, read both axes, to know what is measured and in what units. Third, read the legend, to match each colour with a series. Fourth, find the highest value, the lowest value and the overall trend. Fifth, compare the series and write one clear conclusion.

Let us apply the steps to the canteen chart. The tallest bar is March tea, at four hundred fifty cups. The shortest bar is April samosas, at two hundred fifty. The trend is up in March, then a sharp fall in April. In every month, the tea bar is taller than the samosa bar. So one conclusion is, the canteen should stock less in exam months.

Each chart type answers a different question. In a column or bar chart, compare bar lengths to find the most and the least. In a line chart, look at the slope, because a line going up means a rise. In a pie chart, find the biggest slice, which shows the largest share of the whole. In a scatter chart, dots forming a band mean the two values are linked.

Be careful, because a chart can mislead. Sometimes the vertical axis starts at, say, two hundred instead of zero. Then a small difference of fifty cups looks like a huge gap. So always check the numbers on the axis before you judge the bars. Also, the slices of a pie chart must add up to one hundred percent, or the chart is wrong.

Now, formatting. First, select the exact part you want to change, like one data series or the title. In Excel, right click that part and choose its Format option, such as Format Data Series. A Format pane opens on the right side of the screen, with fill, border and size settings. In LibreOffice Calc, double click the chart to enter edit mode, then double click the part.

Here is what you can format and why. Give the chart title a clear font and a bigger size. Give each data series its own distinct fill colour. Set the axis minimum, maximum and units, so the scale is honest. Turn on data labels when the reader needs exact numbers. Move the legend to the top or the right to save space. Remove or lighten gridlines, so the chart looks less cluttered.

Excel also has quick options on the Chart Design tab. Chart Styles apply a ready made look with one click. Change Colors applies a matching set of colours. Quick Layout adds the title, legend and labels together in one step. In a report, keep the same style for every chart, so they look like one set.

Time to pause and think. Suppose the vertical axis of our chart starts at two hundred fifty, not zero. The April samosa bar, at exactly two hundred fifty, now looks almost invisible. Did samosa sales nearly stop in April? No. The canteen still sold two hundred fifty samosas, and only the axis made it look like zero. Fix it by setting the axis minimum back to zero.

Remember four rules for a good chart. Write a clear title with the topic and the time period. Label the axes with units, like Cups sold. Use only a few colours, and make them easy to tell apart. Avoid three dimensional effects, because they make bars hard to measure.

Let us revise what we learned today. To interpret a chart, read the title, the axes and the legend, and then the trend. Find the highest and lowest values, and write one conclusion. Always check the axis scale, because a chart can mislead. To format, select a part, right click and choose its Format option. Keep a clear title, labelled axes and only a few colours. Next time you see a chart in a newspaper, read it with these steps.