Public Speaking: Using Evidence - Statistics and Testimony

Chapter 8 Review: The Trifecta of Evidence

Commemorative Speeches

  • Topics for commemorative speeches will be pitched this coming Friday.

Review of Chapter 8: Examples, Statistics, and Testimony

Examples
  • Purpose: Used to evoke pathos (emotional appeal) in speeches.
  • Types: Brief examples, hypothetical examples, and extended examples.
Statistics
  • Context is Crucial: Statistics must always be analyzed within their specific context.
    • The way a metric is defined significantly alters interpretation (e.g., "healthy" bread, "fastest" animal).
    • Emphasizing "as much as 5%5\%" versus "just 5%5\%" changes perception.
    • Examples: Cheetah (fastest over short distances) vs. Pronghorn Antelope (fastest over long distances).
  • Ethical Use and Critical Thinking: Use statistics ethically, report numbers accurately, and critically evaluate the source and presentation of statistics.
  • **Presidential Salaries Example (Page 139139):
    • Raw Figures:
      • 19421942 (FDR): $75,000\$75,000
      • 19821982 (Reagan): $200,000\$200,000
      • 20222022 (Biden): $400,000\$400,000
    • Contextual Adjustment: When adjusted for inflation, FDR earned the most, and Biden earned the least.
    • Analogy: Comparing highest-grossing movies (e.g., Avatar) without adjusting for inflation vs. older films like Titanic or Gone with the Wind in their heyday.
    • Principle: Raw numbers alone are insufficient; full context is required.
  • Representativeness: Statistics must be representative of the population or phenomenon being studied.
    • Autism Study Example: A highly publicized study linking vaccines and autism was found to be based on a very small, unrepresentative sample (under 2020 kids in Scandinavia), leading to widespread skepticism and misinformation.
    • Bellarmine Parking Survey Example: Surveying DSU (dining hall) diners about parking issues at Bellarmine is not representative, as commuters (who face parking issues) may not eat on campus.
    • Baseball Player Example: Claiming all baseball players are smart based on a son's team is not representative; it's a small, anecdotal sample.
  • **Statistical Measures (Mean, Median, Mode):
    • Mean: The average value of a group of numbers.
      • Calculation: Sum of all values divided by the number of values (∑xn\frac{\sum x}{n}).
      • Weakness: Not resistant to outliers (e.g., a 100100 and a 00 on a test, or high salaries of top athletes), which can disproportionately skew the data.
    • Median: The middle figure in an ordered group of numbers.
      • Method: Order data from highest to lowest and select the middle number. For 2121 data points, the 11th11^{th} number is the median (with 1010 above and 1010 below).
      • Strength: More resistant to outliers than the mean, often providing a more representative statistic.
    • Mode: The number occurring most frequently in a group.
      • Application: Useful in business (e.g., identifying popular products like value meal #44 or a specific SKU of clothing).
    • **Textbook Examples (Page 140140 - Group A & Group B):
      • **Group A (Numbers: 7,500,6,300,5,000,4,400,4,4007,500, 6,300, 5,000, 4,400, 4,400):
        • Median: 5,0005,000
        • Mean: (7,500+6,300+5,000+4,400+4,4007,500 + 6,300 + 5,000 + 4,400 + 4,400) /5/ 5
        • Mode: 4,4004,400
      • **Group B (Numbers: 5,000,5,000,5,000,5,000,5,0005,000, 5,000, 5,000, 5,000, 5,000):
        • Median: 5,0005,000
        • Mean: (5,000×55,000 \times 5) /5=5,000/ 5 = 5,000
        • Mode: 5,0005,000
      • Observation: The median can be the same for different data sets, while the mean and mode vary significantly, highlighting the importance of understanding each measure.
  • **Tips for Using Statistics Effectively:
    • Reliable Source: Statistics must come from a reliable source.
      • Concern: Politicization of institutions like the CDC, where studies might be suppressed if they don't align with political policies.
      • Bias Awareness: Understand the inherent bias of organizations (e.g., political administrations presenting favorable economic data) but rely on reputable sources like the IMF, NIH, or Gallup polls.
      • Transparency: Always identify the source of the statistics.
    • Quantify Ideas Sparingly: Use statistics strategically and sparingly.
      • "Fewer is better"; one or two well-placed numbers are more impactful than a deluge.
      • Example (Page 141141 - Healthcare): Listing numerous complex statistics (life expectancy 46th46^{th}, infant mortality 52nd52^{nd}, $3.2 trillion\$3.2 \text{ trillion} spent, 17.8%17.8\% of GDP, 50th50^{th} in efficiency) can overwhelm the audience and dilute the message.
    • Identify the Source: Clearly state where the statistics come from (e.g., Los Angeles Times, not vague "sources in the White House"). This enhances credibility.
    • Explain the Relevance: Put raw numbers into context using examples, analogies, or vivid imagery to make them meaningful to the audience.
      • Skipping Class Analogy: Instead of just losing money, equate missing class to:
        • Setting fire to $70\$70.
        • Throwing a $70\$70 video game in the trash.
        • Missing four Taco Bell meals ($13/meal×4 meals≈$52\$13/\text{meal} \times 4 \text{ meals} \approx \$52 of wasted money).
      • Hurricane Harvey Example (Page 142142): Instead of "28,00028,000 square miles," say "an area larger than Lake Michigan" to provide a relatable scale.
      • Trillion Dollars Example: Explaining that a trillion dollars is enough to give every American a new $3,000\$3,000 car and still have money left over graphically illustrates its magnitude.
      • Refugee Crisis Example: Instead of "22.522.5 million refugees," state "more than the population of America's five biggest cities combined (New York, Los Angeles, Chicago, Houston, and Phoenix)" to contextualize the scale for an American audience.
    • Round Off Statistics: Round numbers for easier comprehension and retention, unless a precise figure is compellingly necessary for dramatic effect (e.g., Mia Hamm's "60,24860,248 eyeballs").
      • Examples: Instead of "Mount Everest is 29,02929,029 feet high," say "about 29,00029,000 feet."
      • Instead of "population of Germany is 84,341,09284,341,092 people," say "over 8484 million people."
    • Use Visual Aids: Graphs and charts enhance understanding.
      • Line graphs: Good for trends over time.
      • Bar graphs: Good for comparisons.
      • Pie charts: Good for percentages.
      • Infographics: Simple visuals (e.g., an arrow on a house for housing prices) make statistics more palatable and digestible.
Testimony
  • Definition: Quotations or paraphrases used to support a specific point.
  • Types:
    • Expert Testimony: From recognized authorities (e.g., college president, doctor, store manager, teacher). Lends ethos (credibility).
    • Peer Testimony: From ordinary people with firsthand experience (e.g., a student regarding FAFSA, a cancer patient about health research impact). Evokes pathos (emotion).
  • **Tips for Using Testimony:
    • Direct Quotes: Present testimony word for word (e.g., from voice memo recordings). Full-sentence quotes are generally more effective than partial quotes.
    • Not Out of Context: Ensure quotes are not distorted by taking them out of their original context. This is an ethical imperative (e.g., quoting "I can't wait to get out of here" from a student who loves Bellarmine but is just homesick for Thanksgiving is unethical).
    • Paraphrase: Summarize testimony in your own words if it's too long, unclear, or can be stated more effectively. Still requires oral citation.
    • Quote/Paraphrase Accurately: Always maintain the original meaning.
    • Use Qualified Sources: Ensure the source has expertise relevant to the topic (e.g., Jennifer Aniston for acting/fame, not offshore drilling; Leonardo DiCaprio for environmental causes).
    • Use Unbiased Sources: Be wary of sources with a vested interest (e.g., pharmaceutical companies promoting their drugs, toothpaste brands promoting their products).
    • Identify Sources: Provide not just the name but also the context or qualifications of the source (e.g., "Mary Flanagan, a pediatrician in Louisville for the last 4040 years"). Do not assume the audience knows who someone is unless they are universally famous (e.g., Beyoncé, Travis Kelce, Tom Brady).
    • Oral Citation:
      • Goal: Be fluid and conversational while providing sufficient information for credibility.
      • **Example from textbook (Page 142142):
        • "The Minneapolis Star Tribune of 01/31/201801/31/2018 quotes Chris Nowinski, cofounder of the Concussion Legacy Foundation on the dangers of youth tackle football. 'Children,' he says, 'were never intended to be hit in the head 500500 times in three months every year while the brain is going through incredible development.'"
        • Critique: This is a bit long and not conversational.
        • Streamlined: Focus on the newspaper (Minneapolis Star Tribune as a credible source), the expert's name (Chris Nowinski), and their affiliation (Concussion Legacy Foundation). The exact date is often unnecessary in an oral citation.

Exercises for Critical Thinking (Page 153153)

  • Instructions: Identify the flaw(s) in each statement violating criteria for effective supporting materials.
    • A. "In the words of one expert, the prevalence of online multitasking is reducing the ability of people to concentrate on a single task no matter how important the task might be."
      • Flaw: Did not identify the expert. (Lack of source identification).
    • B. "The average score on the last exam was 7373 percent."
      • Flaw: Implies "average" is the mean, but often the median is more representative; the specific statistical measure is not clearly identified or contextualized. If an outlier skewed the data, the mean may not be the most appropriate