Google says that the margin of error is “The margin of error is a statistic expressing the amount of random sampling error in a survey’s results. The larger the margin of error, the less confidence one should have that the poll’s reported results are close to the “true” figures; that is, the figures for the whole population.”
But how do they know how wrong they are? Is it just bullshit?
In: Mathematics
Lets assume 2 candidates, A and B, with around 50% support each.
If I ask everyone in the electorate who they’re voting for, my results will be perfectly accurate (unless some of them change their minds), but I can’t do that.
I ask 100 people chosen randomly. Now it’s not improbably that I get exactly 50 people responding each way, but I wouldn’t be surprised if I get a 51/49 split, or even somewhere around a 45/55 split. It just happened that my random choice picked a few extra supporters of 1 candidate or another. Statistics are noisy like that.
We can use mathematical models to work out how likely it is that it’s within a range of 1% or 5% or whatever. With 100 people we can say that 90% of the time we’re accurate to within a range of 6%, 95% of the time we’re accurate within 9%, and 99% of the time accurate to within 12%.
By convention we look at what we can be 95% certain of. This is just a convention. We find that if we randomly select 1000 people, 95% of the time the number falls within 3%.
Be aware that this means that 5% of the time, we’re going to be outside that 3% range. So it’s always worth taking statistics with a pinch of salt.
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