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Chapter 11: Being Credible and Using Evidence
Chapter Objectives and Integrator Guide
After reading and thinking about this chapter, students should be able to meet the
following objectives.
Objectives
1. Explain the importance of source credibility in public presentations.
Key term: source credibility
2. Use fours dimensions of credibility to improve how audience members perceive you.
Key terms: competence, trustworthiness, dynamism, common ground, sleeper effect
3. Develop a research strategy for finding support for your presentation.
Key terms: personal experience, reference librarian, search engine, heuristics
4. Use research to identify eight types of supporting materials for your ideas.
Key terms: bibliographic reference, internal reference, verbal citations, supporting
material
5. Correctly attribute information to sources, both verbally and in writing.
Key terms: supporting material, examples, narratives, surveys, testimonial evidence, lay
testimony, expert testimony, celebrity testimony, statistics, analogy, explanation,
definitions
6. Ground your use of credibility and supporting materials in core ethical principles
surrounding honesty.
Key terms: plagiarism, incremental plagiarism, two-sided argument
Activities
Activity 11.1 Credibility of Others
Objectives
Students should be able to identify sources that are highly credible to them; to name the
factors that affect credibility; and to discuss why credibility is a function of the audience and
not the speaker.
Procedure
Distribute copies of the “How Credible Are These Sources?” form found on the following
page to all of the students, and have them complete it according to the directions given.
Class Discussion
When everyone has completed the form, ask for a show of hands and sum up the ratings on
the board. The students should compare the ratings of each source by topic. Differences in
ratings on different topics should be noted and explained. The students should also note
differences among their classmates’ ratings of the same source in the same topic. The
students should reach the conclusion that credibility is a function of the audience’s
perception of the speaker, not an inherent quality of the speaker. The reasons for the ratings
should be ascertained.
Applications
This activity demonstrates the nature of credibility. The credibility of a speaker varies with
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How Credible Are These Sources?
Examine the sources on this form, and indicate whether or not you think each source is credible
for each of the following topics:
A. Religion
B. Education
C. Human relations
D. Economics
E. Politics
Mark each source with a number according to the following scale:
1. Not credible
2. Average credibility
3. Highly credible
Each column on the form represents one of the five topics listed. Be sure to rate each source on
each topic.
A
B
C
D
E
Your father
Your speech teacher
A philosophy teacher
A millionaire
A medical doctor
Your university president
A small-business person
Your state senator
A psychiatrist
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Activity 11.2 Expert Interview
Objective
Students should be able to recognize the value of interviewing and utilizing information
gleaned from an interview for a public speech.
Procedure
Divide the class into dyads and instruct them to choose one of the speech topics found
in chapters 10, 14, and 15 of the text. Each dyad is to conduct an interview based on the
chosen topic. As a team, the individuals should discuss some potential questions from the
interview without any information from which to draw. Therefore, the instructor should
address the importance of securing research and supporting materials prior to interviewing
someone on a particular topic. Class interaction should then assess the value of using the
interview format in obtaining expert information and opinion on a topic.
Applications
This activity has obvious relevance to information on interviewing found in chapter 9.
The activity also illustrates that finding information for a speech can include more than just
library research.
Activity 11.3 Establishing Credibility
Objectives
Students should be able to demonstrate the ability to establish their own credibility, relating
the demonstration to each of the aspects of credibility; to discuss the differences and
similarities of the aspects of credibility; and to describe ways in which the introduction to a
speech can help to establish a speaker’s credibility.
Procedure
during the delivery phase of the exercise.
After each student has prepared an introduction, divide the students into groups of five. Each
the speaker’s credibility. A list of phrases or examples of each aspect of credibility can be
written on the board to help illustrate the various methods by which a speaker can enhance
credibility.
Applications
This activity is preparatory to delivering a classroom speech. It illustrates the aspects of
credibility and the strategies for establishing a speaker’s credibility. The students should be
able to practice some of their speech skills during this exercise and thus become more
confident about delivering a complete speech.
Activity 11.4 Verbal and Nonverbal Influences on Credibility
Objectives
Students should be able to discuss the relative contributions of verbal and nonverbal behavior
to credibility; and to define each aspect of credibility in terms of specific verbal and
nonverbal behavior.
Procedure
Show the class a five-minute segment of a videotape recording or film of a public speech
Form” provided below.
Read the following directions to the students after each presentation of the film:
On your “Credibility Rating Form,” indicate how you rate the speaker by writing a
number from 1 (low) to 5 (high) beside each characteristic. For example, if you
think that the speaker was very charismatic, write 5; if only average, write 3; if
between the “sound only” and the “picture only” versions may be especially noticeable. The
students should identify specific verbal and nonverbal behavior that led to their rating of the
speaker on each aspect of credibility. The students usually conclude that much of their
and delivery of the speaker, as well as the verbal content of the speech. The students learn
how to become more credible when they deliver their own speeches to a classroom audience.
They also learn how they judge the credibility of others. The concepts of nonverbal codes
may be reviewed to clarify the discussion of the delivery and the visual elements of the
speech.
Credibility Rating Form
Picture only
Both
Charisma
Co-orientation
Expertise
Trustworthiness
Dynamism
Competence
Sincerity
Commitment
Empathy
Strength
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Activity 11.5 An Important Tour
Objective
Students should be able to secure knowledge of the library to utilize research necessary for
effective speechmaking.
Procedure
one question to ask the librarian. Further, a follow-up discussion should emphasize the value
of seeking any possible outlets for information for a public speech.
Applications
gained from such a tour can aid students in all of their college courses. Moreover, this tour
can provide students specified areas that are directly relevant to public speaking (for
example, reference databases, special collections, interlibrary loan, and so on).
Activity 11.6 Fountain of Knowledge
Objective
Students should be able to realize the value of exploring library resources to discover various
facets of information.
Procedure
Divide the class into small groups of five to seven students. Instruct them that they have
approximately 30 minutes in which to discover answers to questions the instructor composed
(see “Sample Questions” below). These questions should have answers that can be found in
This activity is an excellent follow-up to activity 11.5. The groups should be encouraged to
address how they went about gathering answers and discuss some of the ways in which the
task was easy as well as difficult.
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Applications
This activity illustrates that information is not always found in the customary places students
are likely to consult (electronic book databases, non-academic websites, encyclopedias, and
so on). Students will be able to realize the value of knowing areas of the library to facilitate
the location of research.
Sample Questions
1. Who wrote The Feminine Mystique?
2. Where would I find an illustration of the number of professors in higher education
in 1989?
3. What are the reference materials written by James C. McCroskey?
4. Who was the originator of the phrase “A penny saved is a penny earned”?
5. How much did the Chrysler Corporation earn in profits in 1988?
6. In 1989, which periodicals addressed teacher shortages?
7. Find testimony on the value of reducing cholesterol levels.
8. Cite the recent books/journal articles by communication researcher Gerald Miller.
9. Who was the first black college graduate in the United States and from what school
did he/she graduate?
10. What are the underlying principles guiding Amnesty International?
Activity 11.7 Researching the Topic
Objectives
Students should be able to identify the primary and secondary sources for research into a
specific topic; to prepare a bibliography of several different resources; and to demonstrate a
familiarity with library and Internet sources by researching a specific topic.
Procedure
Tell the students to select and limit a topic and to write a statement of immediate purpose for
the topic. They should then prepare a bibliography of primary and secondary sources for the
topic. The bibliography should include references from encyclopedias, newspapers, journals,
popular magazines, websites, interviews (names of people who could be interviewed), and
personal experiences (a synopsis). Ask the students to bring their bibliographies to class.
Class Discussion
The students should discuss any problems they encountered while preparing the
bibliography, such as locating materials, using the library, or using specific reference
sources. They should also share shortcuts or timesaving procedures for finding or using
reference materials. A review of interview procedures may encourage students to use
interviews as a primary source.
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Applications
This activity is designed to acquaint the students with a variety of source materials available.
The students also gain practice in using resources to research a topic. The material gathered
for this activity may be used as resource materials for a classroom speech.
Activity 11.8 Using Statistics
Objectives
Students should be able to define the statistical terms used to summarize or describe
numerical data; to derive statistical data from raw numbers or information; and to decide
which statistics are best suited for presenting certain types of information.
Procedure
Distribute the following “Which Statistic Do I Use?” questions and instructions to each
student to answer individually. The students may refer to the text as often as necessary to
answer the questions.
Which Statistic Do I Use?
For each of the items that follow, indicate which statistic you would use to most
effectively present the information to an audience of your classmates. In other words,
which method of presenting the information is most accurate, most descriptive, and most
easily understood by your audience?
1. If you had all the grades for all the seniors at two major universities, how would you
compare the abilities of the students at the two schools?
2. The price of new cars in the United States rose from an average of $4,000 in 1970 to
$5,000 in 1978. How would you present this information?
3. What statistics would be most relevant if you were trying to tell your classmates how
they compared to each other on a 50-point examination.
4. Assume that there were 456,786 deaths and 478,269 births in the United States last
year. How would you inform the audience of the growth or decline of the population?
5. A survey shows that 35 of 50 students prefer the quarter system and that the other 15
students prefer the semester system. How would you inform the audience of the
students’ preferences?
6. If the numbers in the following list indicate the number of people in the immediate
families of some of your classmates, explain how you would inform the class of the
most common family size: 3, 1, 3, 3, 4, 7, 3, 2.
7. How would you indicate the variance in temperatures in your state in the last 30
years?
Class Discussion
The correct answers to the questions are given below. Discuss the answers with the students
and then have them explain the reasons for their personal answers. If they disagree or do not
understand the reasons for using one statistic instead of another, have them answer with
different measures to see which is best understood by the audience. The students should be
able to define each of the statistical terms and to discuss its uses in summarizing and
describing data. They should also be able to point out ways in which statistics can be used to
mislead an audience.
Answers
1. Use the grade point mean, or average for each school. If the schools were very
dissimilar, it would also be appropriate to state the mode and range of each
distribution.
2. Use a percentage: an increase of 25 percent. Also use the dollar numbers and state the
Applications
This activity allows students to practice adapting supporting materials to a specific audience.
It also familiarizes them with the use of statistical data, which may be helpful in preparing an
informative or a persuasive speech, as well as in becoming a more critical audience member.
Activity 11.9 Adapting Supporting Materials
Objectives
Students should be able to discuss factors that affect the choice of evidence and supporting
materials; to analyze the sources and content of evidence in relationship to a specific
audience; and to decide what types of evidence will be most credible to an audience.
Procedure
Distribute the “Would You Use This Material?” form that follows to each student to
complete individually.
Class Discussion
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the kinds of supporting material mentioned in each instance. Compare the predictions with
the stated preferences.
The students should explain the reasons for their predictions using the audience analysis
activities they completed earlier. They should be able to justify their predictions with specific
references to the audience analysis. For example, if a large number of the students in the
source or validity of the information? Students should also discuss alternative ways of
presenting the same information. Statistics can be presented orally or on a chart or graph, as
approximations, percentages, or raw numbers. The students should decide which method of
presentation the audience is most likely to listen to and which method will best help the
audience to remember the material presented.
understand. This activity is also helpful to the students in preparing a classroom speech.
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Would You Use This Material?
Examine the supporting materials listed. Using the information gained from your previous
analysis of the class as an audience, decide which materials would be appealing or unappealing
to your classmates. Be prepared to justify your answers.
Appealing
Unappealing
_________
_________
1.
Pictures and illustrations of junk food
_________
_________
2.
A quotation from a local physician against smoking
_________
_________
3.
A survey of the smoking habits of your class
_________
_________
4.
An interview with a drug counselor about drug abuse
_________
_________
5.
Your personal experience as a camp counselor
_________
_________
6.
A research study of the dating habits of college students
_________
_________
7.
Statistical summaries of the most popular records in the
last decade
_________
_________
8.
The percentage of your classmates who are living off-
campus
_________
_________
9.
A bar graph showing how much money can be saved by
buying savings bonds
_________
_________
10.
Testimony from six students about the cost of owning a car