No matter what comparisons or trends you plan to discuss in your presentation, you’re going to use one of five charts to show it: a pie chart, bar chart, column chart, line chart or dot chart. Almost every sales rep is familiar with these ubiquitous chart forms, but few know how to use them correctly and appropriately. In the Say It With Charts Complete Toolkit (McGraw-Hill, 2007), Gene Zelazny explains each chart and the type of data for which it is best suited. Here’s a look at each one.

1. Pie chart. The pie chart is the most popular chart, but it shouldn’t be, says Zelazny. It is the least practical of the five charts and should account for less than 5 percent of the charts you use. It is best used for component comparisons – a comparison which shows the size of each part as a percentage of the total. For instance, if there were five companies that made up a certain industry and you wanted to show their share of industry sales, a pie chart would be appropriate. “Any time your message contains words such as share, percentage of total, accounted for x percent, you can be sure you’re dealing with a component comparison,” says Zelazny.

2. Bar chart. This chart uses bars extending horizontally across the chart. It is the “least appreciated” of the charts and should account for as much as 25 percent of all charts used in your presentation, says the author. Bar charts should be used for item comparisons, when you want to compare how things rank. Words like larger than, smaller than or equal are indicative of an item comparison. Each horizontal bar is a separate item – sales, companies, countries, individuals, and so on. To identify the value of each bar, use either a scale at the top or numbers at the ends of the bars, but not both.

3. Column chart. Similar to the bar chart, the column chart uses vertical bars to illustrate its data. The column chart and the line chart are the “workhorses” of your presentation and the two should account for half of all charts used. Column charts are best used for time series comparison where the primary goal is to show how things change over time. While line charts do the same thing, the difference is that column charts “emphasize levels or magnitudes and are more suitable for data on activities that occur within a set period of time, suggesting a fresh start for each period.” Column charts are also appropriate for frequency distribution comparisons, which show how many items fall into a series of progressive numerical ranges (for instance, the number of employees earning less than $25K, earning $25K – $50K, earning $50K – $75K, and so on). In this application, column charts are good for summarizing vast amounts of data to demonstrate some meaningful relationship. They are best when five to seven ranges are shown. If there are more, a line chart is better.

4. Line chart. The line chart is just that – a line that shows a trend over time. Like the column chart, line charts are best for time series comparison and frequency distribution comparison. But there’s one major difference: “A line chart emphasizes movement and angles of change,” says Zelazny. Thus is it the best form for showing data that have a “carry-over” from one time to the next, such as inventory data.

5. Dot chart. Sometimes called a scatter chart or scatter diagram, the dot chart looks intimidating at first glance but “has its place 10 percent of the time,” says the author. Its best use is for correlation comparisons, which, he says, show “whether the relationship between two variables follows – or fails to follow – the pattern you would normally expect.” When your message includes words such as related to, increases with, decreases with, changes with, varies with (or the converse, such as doesn’t increase with, etc.), you’re dealing with a correlation comparison. In the dot chart, a line showing the expected pattern should be drawn so the audience can see where the plotted points fall in relation to that line. Say, for instance, you want to show the correlation between units sold and discounts offered. If the data points cluster around the “expected pattern” line, you’d show that as discounts increase, unit sales increase. However, if the dots were scattered, you’d show that the size of the discount has little or no effect on volume purchased.

Now that you have a basic understanding of each of the five charts and when they should be used, go back and take a look at your presentation. Have you used a pie chart when you should have used a bar chart? Could all the text on a slide be more convincingly represented with a dot chart? Is each chart absolutely essential to the central message of your presentation? By evaluating each chart with a fresh eye, you’ll ultimately give your data greater impact and meaning.