Election polls for the numerically challenged


Toronto is in the midst of a heated contest with two major mayoral candidates, Rob Ford and George Smitherman. Which means we’re going to hear a lot of numbers being thrown at us. So here is a quick and easy guide to what those numbers mean.

In this case, a poll means that a bunch of people have been asked who they will vote for, perhaps hundreds or thousands of people. Maybe you find out that 30% plan to vote for one person and 35% plan to vote for the other.

When you ask only a few hundred people who they will vote for, you have a bigger chance of making a mistake than if you ask thousands. Pollers call that chance of mistake the margin of error. I call it the jiggle factor.

So, the 30% and 35% are jiggly numbers. If you only ask a few hundred people in your poll, those numbers will jiggle a lot. If you ask thousands of people, the numbers won’t jiggle a lot.

With a margin of error, or jiggle factor, of 3 points, the 30% might jiggle as low as 27% or as high as 33%. And, the 35% might jiggle as high as 38% or as low as 32%.

See how we applied the jiggle factor(margin of error) to both numbers? It means that the low number is actually somewhere between 27 and 33 and the high number is actually somewhere between 32 and 38. Notice that those two sets of numbers overlap on 32 and 33. This tells you that the 30% and the 35% are not different from each other and that our two candidates are in a dead heat.

Even though the one number is 5 points larger than the other number, they really are equal to each other. The important part is to apply the jiggle to both numbers.

In the end, the only way to know if they are different is to vote. So vote!

(It’s a lot more complicated than this, but hopefully the general idea is clear.)

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