I’ve noticed most U.S. polls query around 1,000 people and sometimes even less. Somehow that qualifies for headlines like “Americans say…” or “Most Americans…” How is it acceptable that 0.0002% of the population is accepted as representative?
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Whether a sample is representative does not depend on the size of the overall population, at least once the population gets large enough. A random sample of 1000 people out of one million or one billion or one trillion still yields a margin of error of approximately 3 percent – which means that 95% of the time, the true sentiment if you measured everybody would be within three percentage points of your random sample.
The hard part is getting a random sample. If you poll a church in East Texas, you’ll get a very different response than on the wharf in San Francisco. If you poll online, you might miss those that don’t have internet access, and that will swing things, both by geography and demographics.
So 1000 of the right people is representative, but getting that 1000 is very hard to do.
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