Public Speaking

Use Statistics Carefully (^101)
in 2015 increases its hiring at a rate of 50 percent. However, a company that employs
100 people in 2014 and adds one additional employee in 2015 increases hiring by
1 percent. The actual number of additional employees is the same in each company, but
the rates of increase are dramatically different. The reverse is also true: A two-person
company that loses one employee decreases by half or 50 percent; there’s barely a blip
when a larger company loses one worker. As you can see, when baseline numbers are
initially very low, the rate of increase is potentially astounding.
Relationships between numbers are often shown as a ratio, instead of a percentage
because 10 percent and 1 in 10 are interchangeable; similarly, you could state 60 percent
as 3 out of 5. Ratios are especially helpful when the percentage is very small; for example,
0.000018 percent equals 18 cases per 100,000. You can see that it’s more effective to say,
“The study found that suicide rates were 18 out of 100,000 in rural areas and 13 per
100,000 in urban areas,” than to say “thirteen-hundred-thousandth of 1 percent of
urban residents.”^16

Use Visual Aids to Clarify Numerical Data

Because numerical data can be complex, present them in visual form whenever you can.

Imagine trying to understand a speaker who simply said:

The cost of living varies by region. According to CNN Money, what you can buy

for $50,000 in Portland, Oregon, would cost $97,700 in Manhattan and $69,200 in

San Francisco but only $40,900 in Las Cruces, New Mexico, $39,300 in Des Moines,

Iowa, and only $35,200 in Norman, Oklahoma.^17

Would you remember any of these data? Now, imagine that the speaker provides a

visual with Table 8.1 on it. How does the visual help you grasp the material more easily?

Obviously, different types of data call for different types of visuals, but graphs and

tables are especially good for projecting numerical data. (Chapter 13 explains how

to create and display visual materials.) A table such as this one, comparing living costs

in several cities, effectively depicts numerical data in a format that listeners can easily

grasp.

Critically Analyze Numerical Data

Because numbers are easy to manipulate, evaluate them carefully with these questions

before you use them.

ratio relationship shown by

numbers, such as 1 in 10

table 8.1

Comparative Cost of Living by Region

Portland, Oregon $50,000

Manhattan $94,700*

San Francisco $69, 200

Las Cruces, New Mexico $40,900

Des Moines, Iowa $39,300

Norman, Oklahoma $35, 200

*numbers are rounded

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