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Most people (especially in Western society) require some type of evidence, usually in the form of facts and statistics, before they will accept someone else’s claims or position.⁹ Facts represent documented occurrences, including actual events, dates, times, people, and places. Listeners expect the speaker to provide independent verification of facts, so check that you back up factual statements with credible evidence. Statistics are quantified evidence that summarizes, compares, and predicts things.

Use Statistics Accurately

Statistics add precision to speech claims, if you know what the numbers actually mean and use terms that describe them accurately.

USE FREQUENCIES TO INDICATE COUNTS A frequency is simply a count of the number of times something occurs:

On the midterm exam there were 8 A’s, 15 B’s, 7 C’s, 2 D’s, and 1 F.

Frequencies can help listeners understand comparisons between two or more categories, indicate size, or describe trends:

USE PERCENTAGES TO EXPRESS PROPORTION A percentage is the quantified portion of a whole. Percentages help audience members easily grasp comparisons between things, such as the unemployment rate in several states:

In April 2011, Nevada had the highest rate of unemployment, at 12.1 percent. The figure for Alabama was 9.6 percent; for Connecticut, 9.1 percent; and for Wyoming, 6 percent.¹³

Describing the number of males and females in the 2010 Rhode Island population in percentages, rather than in counts (as in the previous section), shows more clearly and quickly the relationship between the two amounts: 48 percent male and 52 percent female.

USE AVERAGES TO DESCRIBE TYPICAL CHARACTERISTICS An average describes information according to its typical characteristics. Usually we think of the average as the sum of the scores divided by the number of scores. This is the mean, the arithmetic average. But there are two other kinds of averages—the median and the mode.

Consider a teacher whose nine students scored 5, 19, 22, 23, 24, 26, 28, 28, and 30, with 30 points being the highest possible grade. The following illustrates how she would calculate the three types of averages:

The following speaker, claiming that a rival organization misrepresented the “average” tax rate, illustrates how the inaccurate use of averages can distort reality:

The Tax Foundation determines an average [mean] tax rate for American families simply by dividing all taxes paid by the total of everyone’s income. For example, if four middle-income families pay $3,000, $4,000, $5,000, and $6,000, respectively, in taxes, and one very wealthy family pays $82,000 in taxes, the average [mean] tax paid by these five families is $20,000 ($100,000 in total taxes divided by five families). But four of the five families [actually] have a tax bill equaling $6,000 or less. . . .[Many] analysts would define a median income family—a family for whom half of all families have higher income and half have lower income—to be the “typical family” and describe the taxes paid by such a median-income family as the taxes that typical middle-class families owe.¹⁵

Present Statistics Ethically

Offering listeners inaccurate statistics is unethical. Following are steps you can take to reduce the likelihood of using false or misleading statistics:

Use only reliable statistics. Include statistics from the most authoritative source you can locate, and evaluate the methods used to generate the data. The more information that is available about how the statistics came about, the more reliable the source is likely to be.

Present statistics in context. Inform listeners of when the data were collected, the method used to collect the data, and the scope of the research:

These figures represent data collected during 2011 from questionnaires distributed to all public and private schools in the United States with students in at least one of grades 9–12 in the fifty states and the District of Columbia.

Avoid confusing statistics with “absolute truth.” Even the most recent data available will change the next time data are collected. Nor are statistics necessarily any more accurate than the human who collected them. Offer data as they appropriately represent your point, but refrain from declaring that these data are definitive.