Opinions always differ on the validity of political polls

World of Politics with Harry McGee  –  harrymcgee@gmail.com

The modern opinion poll was created by an American journalist and academic called George Gallup, who, back in the 1930s, came up with the idea of a scientific sample of the population that would disclose what the entire population was thinking.

Soon Gallup was a very rich man and his company was polling on every imaginable issue, from politics to which washing detergent went down best with the public.

How accurate are opinion polls? On the face of it, they seem to be compelling.

If you take a sample of young people, old people, country people, city people, young and old, rich and poor, west coast, east coast, married, single and other, their display of views should more or less mimic the rest of the population. Over time, mathematical formulae were applied to it.

A simple random sample of 1,067 cases has a margin of error of plus or minus three percentage points for estimates of overall support for individual candidates.

The idea behind confidence levels and margins of error is that any survey or poll will differ from the true population by a certain amount.

So that’s the first get-out clause. If Fine Gael is showing at 30 per cent, that can mean its true support could be as high as 33 per cent or could be as low as 27 per cent.

What’s more pollsters divide results into sub groups. For example, Fine Gael might enjoy support of 35 per cent among 18 to 24 year olds. But the sample is so tiny (160) and the margin of error so big (eight per cent) that it’s meaningless.

So while they appropriate the language of science, polls are relatively crude instruments for ‘measuring’ public opinion.

Of course, that’s not even taking into account human psychology or behaviour.

For example, in political polls, young people and minorities tend to vote at much lower rates, so their behaviour necessitates adjustment.

Another factor is that people are sometimes asked questions on something on which they have no strong opinion, one way or the other. Mid-term polls tend to be a little meaningless as most people have given zero thought.

For more, read this week’s Connacht Tribune.