Chapter Eight – Supporting Materials

Using & Understanding Statistics

Statistics are a systematic collection, analysis, comparison, and interpretation of numerical data of data. As evidence, they are useful in summarizing complex information, quantifying, or making comparisons. Statistics are powerful pieces of evidence because numbers appear straightforward. Numbers provide evidence that quantifies, and statistics can be helpful to clarify a concept or highlighting the depth of a problem.

Statistics can be a powerful persuasive tool in public speaking if the speaker appropriately explains their use and significance. It provides a quantitative, objective, and persuasive platform on which to base an argument, prove a claim, or support an idea. Before a set of statistics can be used, however, it must be made understandable by people who are not familiar with statistics. The key to the persuasive use of statistics is extracting meaning and patterns from raw data in a way that is logical and demonstrable to an audience. There are many ways to interpret statistics and data sets, not all of them valid.

We often know a statistic when we find one, but it can be tricky to understand how a statistic was derived.

You may have heard the terms mean, median, and mode during math class. The mean is the arithmetic average for a data set, which is equal to the sum of the numerical values divided by the number of values. You can determine the mean (or average) by adding up the figures and dividing by the number of figures present. If you’re giving a speech on climate change, you might note that, in 2015, the average summer temperature was 97 degrees while, in 1985, it was just 92 degrees. The mode is the value that appears the most often in a data set. The median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. For example, your professors may use these values when discussing exam results with the entire class, to determine how “well” the class performed overall.Averages and percentages are two common deployments of statistical evidence.

When using statistics, comparisons can help translate the statistic for an audience. In the example above, 97 degrees may seem hot, but the audience has nothing to compare that statistic to. The 30-year comparison assists in demonstrating a change in temperature.

A percentage expresses a proportion of out 100. For example, you might argue that “textbook costs have risen more than 1000% since 1977” (Popken, 2015). By using a statistical percentage, 1000% sounds pretty substantial. It may be important, however, to accompany your percentage with a comparison to assist the audience in understanding that “This is 3 times higher than the normal rate of inflation” (UTA Libraries). You might also clarify that “college textbooks have risen more than any other college-related cost” (Bureau of Labor Statistics, 2016).

You are responsible for the statistical information that you deploy. It’s all too common for us as information consumers to grab a quick statistic that sounds appealing, but that information may not be reliable.

Guidelines for Helping Your Audience Understand Statistics

• Use statistics as support, not as a main point. The audience may cringe or tune you out for saying, “Now I’d like to give you some statistics about the problem of gangs in our part of the state.” That sounds as exciting as reading the telephone book! Use the statistics to support an argument.
• Do not overuse statistics. While there is no hard and fast rule on how many to use, there are other good supporting materials, and you would not want to depend on statistics alone. You want to choose the statistics and numerical data that will strengthen your argument the most and drive your point home. Statistics can have emotional power as well as probative value if used sparingly.
• Use reputable sources for the statistics you present in your speech such as government websites, academic institutions and reputable research organizations and policy/research think tanks.
• Beware of unrepresentative samples. In an unrepresentative sample, a conclusion is based on surveys of people who do not represent, or resemble, the ones to whom the conclusion is being applied.
• Use a large enough sample size in your statistics to make sure that the statistics you are using are accurate (for example, if a survey only asked four people, then it is likely not representative of the population’s viewpoint).
• Use statistics that are easily understood. Many people understand what an average is but not many people will know more complex ideas such as variation and standard deviation.
• When presenting graphs, make sure that the key points are highlighted, and the graphs are not misleading as far as the values presented.
• Explain your statistics as needed, but do not make your speech a statistics lesson. If you say, “My blog has 500 subscribers” to a group of people who know little about blogs, that might sound impressive, but is it? You can also provide a story of an individual, and then tie the individual into the statistic. After telling a story of the daily struggles of a young mother with multiple sclerosis, you could follow up with “This is just one story in the 400,000 people who suffer from MS in the United States today, according to National MS Society.”

Common Misunderstandings of Statistics

A common misunderstanding when using statistics is “correlation does not mean causation.” This means that just because two variables are related, they do not necessarily mean that one variable causes the other variable to occur. For example, consider a data set that indicates that there is a relationship between ice cream purchases over seasons versus drowning deaths over seasons. The incorrect conclusion would be to say that the increase in ice cream consumption leads to more drowning deaths, or vice versa. Therefore, when using statistics in public speaking, a speaker should always be sure that they are presenting accurate information when discussing two variables that may be related. Statistics can be used persuasively in all manners of arguments and public speaking scenarios—the key is understanding and interpreting the given data and molding that interpretation towards a convincing statement.

Putting Statistics into Context for Our Audiences

Graphs, tables, and maps can be used to communicate the numbers, but then the numbers need to be put into context to make the message stick. As the Heaths state:

Statistics are rarely meaningful in and of themselves. Statistics will, and should, almost always be used to illustrate a relationship. It’s more important for people to remember the relationship than the number.

In their book, the Heaths give several good examples of others who have done this. For example, they introduce us to Geoff Ainscow, one of the leaders of the Beyond War movement in the 1980s.

Ainscow gave talks trying to raise awareness of the dangers of nuclear weapons. He wanted to show that the US and the USSR possessed weapons capable of destroying the earth several times over. But simply quoting figures of nuclear weapons stockpiles was not a way to make the message stick. So, after setting the scene, Ainscow would take a BB pellet and drop it into a steel bucket where it would make a loud noise. The pellet represented the bomb that was dropped on Hiroshima. Ainscow would then describe the devastation at Hiroshima. Next, he would take 10 pellets and drop them in the bucket where they made 10 times as much noise. They represented the nuclear firepower on a single nuclear submarine. Finally, he poured 5,000 pellets into the bucket, one for each nuclear warhead in the world. When the noise finally subsided, his audience sat in dead silence.

That is how you put statistics into context.

Using Tables, Graphs and Maps to Communicate Statistical Findings

The story of communicating your statistics does not end with putting them into context. Actually, it would be better to say that it does not begin with putting the numbers into context. In reality, the story you are telling through your evidence will probably start with the display of a table, graph, or map.

A simple table, graph, or map can explain a great deal, and so this type of direct evidence should be used where appropriate. However, if a particular part of your analysis represented by a table, graph, or map does not add to or support your argument, it should be left out.

While representing statistical information in tables, graphs, or maps can be highly effective, it is important to ensure that the information is not presented in a manner that can mislead the listener. The key to presenting effective tables, graphs, or maps is to ensure they are easy to understand and clearly linked to the message. Ensure that you provide all the necessary information required to understand what the data is showing. The table, graph, or map should be able to stand alone.

Tables, graphs, and maps should:

• relate directly to the argument;
• support statements made in the text;
• summarize relevant sections of the data analysis; and
• be clearly labelled.

Table Checklist

• Use a descriptive title for each table.
• Label every column.
• Provide a source if appropriate.
• Minimize memory load by removing unnecessary data and minimizing decimal places.
• Use clustering and patterns to highlight important relationships.
• Use white space to effect.
• Order data meaningfully (e.g., rank highest to lowest).
• Use a consistent format for each table.

Also, do not present too much data in tables. Large expanses of figures can be daunting for an audience, and can obscure your message.

Graph Checklist

• Title: Use a clear, descriptive title.
• Type of graph: Choose the appropriate graph for your message, avoid using 3D graphs as they can obscure information.
• Axes: Decide which variable goes on which axis, and what scale is most appropriate.
• Legend: If there is more than one data series displayed, always include a legend, preferably within the area of the graph.
• Labels: All relevant labels should be included.
• Color/shading: Colors can help differentiate; however, know what is appropriate for the medium you’re using.
• Data source: Provide the source of data you’ve used for the graph.
• Three-Quarters Rules: For readability, it’s considered best practice to make the y-axis three-quarters the size of the x-axis

Using Testimony

A testimony is a statement or endorsement given by someone who has a logical connection to the topic and who is a credible source.

Testimony can be used to either clarify or prove a point and is often used by referring to the research of experts. For example, you could quote a study conducted by an independent auditing organization that endorses your organization’s ability to financially support current workforce levels.

There are three types of testimonials that fall into the range of testimony; knowing your audience leads to the best choice.

• Expert authorities
• Celebrities and other inspirational figures
• Peer

Expert Authorities

First, we can cite expert authorities. According to Chip and Dan Heath in their book Made to Stick, an expert is “the kind of person whose wall is covered with framed credentials: Oliver Sacks for neuroscience, Alan Greenspan for economics [well, maybe not such a great example any longer], or Stephen Hawking for physics.”

If an expert supports our position, it usually adds credibility. If we are giving a presentation on a medical issue and can find support for our position in prestigious medical reviews such as The New England Journal of Medicine or The Lancet, it would probably be a good idea to cite those authorities.

How to Incorporate Expert Testimony

When a claim or point is made during a speech, the audience initially may be reluctant to concede or agree to the validity of the point. Often this is because the audience does not initially accept the speaker as a trustworthy authority. By incorporating expert testimony, the speaker is able to bolster their own authority to speak on the topic.

Therefore, expert testimony is commonly introduced after a claim is made. For example, if a speech makes the claim, “Manufacturing jobs have been in decline since the 1970s,” it should be followed up with expert testimony to support that claim. This testimony could take a variety of forms, such as government employment statistics or a historian who has written on a particular sector of the manufacturing industry. No matter the particular form of expert testimony, it is incorporated following a claim to defend and support that claim, thus bolstering the authority of the speaker.

In using expert testimony, you should follow these guidelines:

• Use the expert’s testimony in their relevant field. A person may have a Nobel Prize in economics, but that does not make them an expert in biology.
• Provide at least some of the expert’s relevant credentials.
• If you interviewed the expert yourself, make that clear in the speech also. “When I spoke with Dr. Mary Thompson, principal of Park Lake High School, on October 12, she informed me that . . .”

What to Consider Before Using Testimony

Before using testimony, ask:

• Is the material quoted accurately?
• Is the source biased, or perceived as biased?
• Is the source competent in the field being consulted?
• Is the information current?

In the end, your choice as to which type of testimony you use will depend on your audience.

Smokers, for example, know all of the hazards of smoking and still continue to smoke. Give them a presentation on the dangers of smoking using expert testimony and you’ll probably be met with a response like, “Yeah, but it won’t happen to me.” Use a peer like Pam Laffin, however, and the response will be totally different.

Here is a young woman who probably also thought that it wouldn’t happen to her, speaking “from her grave.” Smokers can relate to her. She isn’t just a numerical figure. This type of testimony is quite effective when you’re trying to tell people the dangers of doing something.

So, get to know your audience, put yourself in their place, and choose the type or combination of evidence that will make your message stick.