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Part I: Vital Statistics about Statistics
together the pieces independently. A double-blind study is best, because even
though researchers may claim to be unbiased, they often have a special inter-
est in the results — otherwise they wouldn’t be doing the study!
Surveys (Polls)
A survey (more commonly known as a poll) is a questionnaire; it’s most often
used to gather people’s opinions along with some relevant demographic infor-
mation. Because so many policymakers, marketers, and others want to “get
at the pulse of the American public” and find out what the average American
is thinking and feeling, many people now feel that they cannot escape the
barrage of requests to take part in surveys and polls. In fact, you’ve probably
received many requests to participate in surveys, and you may even have
become numb to them, simply throwing away surveys received in the mail or
saying “no” when asked to participate in a telephone survey.
If done properly, a good survey can really be informative. People use surveys
to find out what TV programs Americans (and others) like, how consumers
feel about Internet shopping, and whether the United States should allow
someone under 35 to become president. Surveys are used by companies to
assess the level of satisfaction their customers feel, to find out what products
their customers want, and to determine who is buying their products. TV
stations use surveys to get instant reactions to news stories and events, and
movie producers use them to determine how to end their movies.
However, if I had to choose one word to assess the general state of surveys in
the media today, I’d say it’s quantity rather than quality. In other words, you’ll
find no shortage of bad surveys. But in this book you find no shortage of
good tips and information for analyzing, critiquing, and understanding survey
results, and for designing your own surveys to do the job right. (To take off
with surveys, head to Chapter 16.)
Margin of error
You’ve probably heard or seen results like this: “This survey had a margin
of error of plus or minus 3 percentage points.” What does this mean? Most
surveys (except a census) are based on information collected from a sample
of individuals, not the entire population. A certain amount of error is bound
to occur — not in the sense of calculation error (although there may be some
of that, too) but in the sense of sampling error, which is the error that occurs
simply because the researchers aren’t asking everyone. The margin of error is
supposed to measure the maximum amount by which the sample results are
expected to differ from those of the actual population. Because the results of
most survey questions can be reported in terms of percentages, the margin
of error most often appears as a percentage, as well.

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