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COMM 2045: Types of Evidence

Resources to help with persuasive speech for COMM 2045


Examples help explain, clarify, or illustrate what you are talking about. These are usually very easy to find in your research. There are three types of examples that you can use.

Brief Examples

Because they are short (two to three sentences), they work well in shorter speeches. They will illustrate your point quickly and effectively without digression.

This excerpt from a student speech about Attention Deficit Hyperactivity Disorder shows how to use a brief example:

"A common symptom of ADHD is inattention. A person with this type is easily distracted. For example, my friend, Joan Lilly, asks her son about a book they just read together, but he cannot recall the details because he never listened throughout the story time."

Extended Examples

Extended examples are long and are thus probably best in the Persuasive Speech, the longest speech assigned in this class. To create extended examples, you use a story, an illustration, or a personal anecdote. Apply the storytelling skills practiced in your first speech.

Hypothetical Examples

Hypothetical examples use imaginary situations. They are usually brief, but they engage listeners effectively. For instance, a speaker might say, "Picture an active 5-year-old boy. Instead of listening to you read or give instructions, he can't sit still or focus on what you're saying." Listeners will become involved in your speech as they imagine a busy little boy, or think of a child they know.


Statistics are numbers or percentages. They clarify, prove, or add interest. Instead of using vague terms like "a lot," "tons," "huge," or "many," provide actual figures. Since many people can experience what's called "numbers shock," they might want to stop listening when they hear anything that sounds like math. To prevent this, help listeners to stay focused on your statistics and to understand what they mean.

This excerpt from a student speech about ADHD illustrates how to use statistics: "More and more American children have ADHD, or are being diagnosed with it. According to the Centers for Disease Control and Prevention, a government agency that gathers health data, an estimated 6.1 million children in the U.S. were diagnosed with ADHD in 2016."

In this next example, a speaker does not just tell us that "submarines are really big." Instead, she says, “The U.S. Navy’s largest nuclear submarines, the Ohio-class, are 560 feet long and 42 feet wide. According to Rick Campbell, who spent 30 years in the Navy and is now a writer, these submarines are ‘almost 2 football fields long, 7 stories tall from keel to sail, and wide as a 3 lane highway.’” Notice how she explains the numbers, making them meaningful through comparison. Since some listeners will not easily process the numbers, she helps them develop understand and develop a picture in their minds. (She might further enhance listeners' understanding by defining the term "keel" if her audience does not include sailors. See the discussion below about definitions.)

Notice that in both examples, the speakers name the source of the statistics, crediting the author and showing listeners that the data is credible. Citing sources, these speakers are also providing testimony.


Testimony is what someone says about your topic. This is not quoting a textbook or article, but the words spoken by another person. You can quote or paraphrase those words, but make clear to listeners when you are quoting or not. For instance, share someone's exact words like this, "According to Nashville pediatrician James Stephens, quote '----- [Dr. Stephens' words] ----' unquote." You do not need to conduct an interview to obtain a testimony. You will find testimonies in your research. The three types of testimony are expert testimony, lay testimony, and prestige testimony.

Expert Testimony

Expert testimony is provided by an expert in the topic of your speech. It is used to provide credibility to your speech topic and evidence.
This excerpt from a student speech illustrates using expert testimony: "Army lieutenant Mike Heath, who works as a pharmacy consultant with the Office of Army Surgeon General, said, 'Generally, manufacturers do not need to register with FDA nor get FDA approval before producing or selling dietary supplements.'”

Here is another example: "One cause of ADHD might be smoking during pregnancy. Dr. Alan S. Brown, a professor of psychiatry and epidemiology at New York's Columbia University in New York City, led a study that found mothers who smoke when pregnant, particularly if they smoke heavily, will have 'offspring with a fairly high risk for ADHD.'"

Lay Testimony

Lay testimony is sometimes referred to as peer testimony.  This testimony comes from average or ordinary people who happen to have some experience or knowledge of the topic. These testimonies can add human interest to the speech.  
This excerpt from a student speech illustrates using a lay testimony: "In China, the number eight is the luckiest number. Corrie Dosh, of the Beijing Review, says that 'if you want to get a new phone number in Beijing, be prepared to pay extra if it has the numeral eight in it.'"

Prestige Testimony

Prestige testimony is sometimes referred to as celebrity testimony. This testimony is given by someone famous.  Words of caution about prestige testimony: be sure the celebrity you are quoting has a real connection to the topic, and make sure he or she is still in good standing with the audience. A celebrity's behavior could be detrimental to their credibility.