A key skill for any employee is the ability to present data and use it to persuade audiences. This article explores the different options for displaying data, including bar charts, line graphs, pie charts and pictograms and how to choose the right one to present your data with maximum impact.
What you’ll learn:
- The various formats for presenting data and the pros and cons of each.
- How to select the best visual display method to ensure you communicate your data in the most effective way.
The Basic Concepts
The ability to present raw data as statistics, graphs or charts is particularly important during the problem-solving and decision making process.
Only when data has been collected, processed and re-presented for a specific purpose does it become a statistic. One of the easiest and most common statistical processes is taking raw data and summarising into totals, creating summary figures.
Charts and graphs are often used to show percentages, which are often referred to as proportions. To work out the percentages, follow these three simple steps:
Step One: Calculate the interest:
Step Two: Divide the increase by the original amount:
Step Three: Multiply by 100:
You could be required to use statistics to present the audience with an idea of the average. There are three types of statistical average, each of which offers a different message despite using the same data. The mode reveals the most common value, the median is the middle value and the mean is the total of all values, divided by the number of values.
Once you’ve summarised the raw data into statistics, you can present it in graphical form to your audience. The key to effectively persuading with numbers is to select the type of graph that best displays and supports the message you’re presenting.
Graphs and Charts
As well as bar charts, graphs and pie charts can be used to present data.
What Graphs Show
Comparing the performance of different variables over time, a graph can offer a direct comparison and highlight trends. As with bar charts, it’s important to check the scale of both axes, particularly the vertical, as these can be altered to give a false impression of the data.
Trends are easier to show on a graph as the data forms a series of plotted points, with time shown on one axis and quantity on the other, meaning you can see when something goes up, down or stays the same. As quantities vary from month to month, it can be difficult to spot the trend, which is why a moving average line is recommended. A statistical tool, it smooths out fluctuations, showing the average value over several months and illustrating the trend.
What Pie Charts Show
Showing the relative proportion of a whole, pie charts give a quick and general impression of data. Divided into slices, the overall size of the pie doesn’t change, meaning it’s not suitable for showing growth or difference in size.
More Than One Pie
Multiple pie charts can be used to compare different, but connected data areas, quickly and clearly. For example, one pie could show the proportion of workers from three departments that use one product, and a second could show the proportion that uses another.
Constructing Charts and Graphs
To construct a chart or graph that has maximum impact; decide on the message presented, choose the right type, organise the data and decide on axes and their scale, before filling in the bars, lines or slices and adding labels. Remember bar charts convey relative size, graphs show changes over time, pie charts show proportions and pictograms add impact.
To make the data manageable, break it down into several categories that don’t overlap and are limited in number. Too many categories gets complicated, but too few reduces the impact of the chart. Name the axes before drawing in the data. Finally, add a clear heading that highlights your intended message.
Often used to show performance targets, a graph displays time on the horizontal axis and quantity on the vertical. Use one colour to plot the planned sales, and another for the actual sales, before adding the projected trend onto the end of the actual line, in a third colour. This helps show how things fluctuated over time and compares current performance with past and future targets.
Before you can start to construct a pie chart, you need to determine the categories and calculate proportions, by dividing the category total by the overall total. Multiply the proportion by 360 degrees to determine the angle of the slice, then accurately draw it onto the pie, using either a protractor or a computer. Once the pie has been constructed, label each slice with percentages added, or use a key to identify the slice and percentage.
A pictogram is a chart or graph that uses pictures to enhance the impact of the data on the intended audience. For example, if you’re showing bicycle sales by region, you could use a pie chart and place it in the wheel of a bicycle.
What highlights trends?
A. A bar chart
B. A line graph
C. A pie chart
B. A line graph
A line graph highlights trends while a bar chart conveys relative size and a pie chart shows relative proportions.
Is the median average the most common value?
The median average is the middle value; the mode reveals the most common value and the mean is the sum total of all values divided by the number of values.
Should you check the scales of the axes when interpreting a chart or graph?
You should always check the scale of the axes when interpreting a chart or graph as they can be altered to give a more dramatic, but false, impression of the data.
What do Pictograms do?
A. Show change
B. Show proportions
C. Add impact
C. Add impact
Pictograms are charts or graphs that use pictures to enhance the impact of the data.
What is the percentage increase when £40,000 grows to £64,000?
The percentage increase is 60%.
64,000 – 40,000 = 24,000
24,000 ÷ 40,000 = 0.6
0.6 x 100 = 60%
- Use graphs to show fluctuations over time, highlight trends or make comparisons.
- Use pie charts to show the relative proportions of values.
- Use pictograms to add impact to your data.
Note: Presenting Data
Presenting numerical information is an important skill for any employee…as raw data, statistics, charts and graphs assist with both problem-solving and decision-making.
However, before you create a graphical display, you need to collect and process the relevant raw data…into one of three forms; totals, percentages or averages.
Percentages, or proportions, are calculated in three simple steps:
One, work out how much the value has increased or decreased…for example £75,000 – £60,000 is an increase of £15,000
Two, divide the answer by the original value… £15,000 divided by £60,000 equals 0.25
Three, multiply that answer by 100 to get the percentage…0.25 multiplied by 100 is 25%.
Alternatively, you could calculate the average, of which there are three types…each of which offers a different perspective on the information.
The mode is the most common value, the number that appears most often, the median is the middle value, and the mean is the sum total of the values divided by the number of values.
Once the raw data has been summarised, you can select the chart or graph that best presents your intended message.
Bar graphs can show relative size, movement over time, growth, or frequency…and are used to make comparisons and draw conclusions.
Categorise the data into several manageable groups, that don’t overlap, ensure the vertical and horizontal axes are clearly labelled…and set an appropriate scale.
Alternatively use a graph to show fluctuations over time, highlight trends or compare two sets of data.
Plot a series of points onto the graph, with time on the horizontal axis and quantity on the vertical.
If the value varies, for example from month to month, use a moving average line to smooth out the fluctuation and show the trends.
When interpreting a chart or graph be aware of any adjustments to the scale as this can give the information a different emphasis…such as making increases, or decreases seems more dramatic.
Although not 100% accurate, a pie chart can be used to show the relative proportions of values, as it gives a strong impression.
To calculate the size of each segment, take its individual value and divide it by the overall data total to find the proportion.
Then, multiply the proportion by 360 degrees to find the angle.
Finally, if you want to give your chart or graph more of an impact, make it a pictogram…replacing the bars, lines, or segments with relevant images.
So, to effectively persuade with numbers you need to summarise the raw data, choose the right type of chart or graph, and set an appropriate scale.