Numbers have power

This morning, the front page of the Irish Examiner, which you can see here on Broadsheet (third one down) caught my attention for this headline:

46% back death penalty for child rape

The subheading is “Farmers take hardline on law and order”

The very first line of the the piece underneath is as follows:

The death penalty should be introduced for the crime of raping a child, according to a national opinion poll.

There are several problems with this in my view. I like the Examiner a lot, and the journalist under whose byline this appears, Conall O Fatharta has done quite a lot of interesting reporting in the last few months. But when you’re claiming that a national poll says that the death penalty should be introduced for the crime of raping a child (or, in fact, any crime), then two things are necessary:

  1. the proportion of people (nationally) who support that assertion should be greater than 50% (it’s not in this case, because already, the headline makes it clear that a majority do not); and
  2. the poll should be on the basis of a reasonable sample of the population at large. If you read the piece more closely, however, the poll was limited to farmers.

As such, the headline which the Examiner plonked on top of the story lacks some important detail, and given its position on the front page, that is deeply regrettable.

What do we know about the poll?

The poll was carried out on behalf of (or by) the Irish Examiner and the Irish Creamery Milk Suppliers Association. We do not know (from this report at least) how many farmers were surveyed, and this is important because the journalist has broken down the figures geographically.

Why does this matter?

It matters on several levels, but chief amongst them is that we cannot be certain that a subset of farmers of the ICMSA is representative of the nation as a whole, or, in fact, possibly not even of farmers in general. For example, a simple question we could ask is was it done on the basis of ICMSA membership and in that case, given the that the ICMSA respresents predominantly dairy farmers, is it safe to say the output from a survey of dairy farmers applies to all other farmers.

An additional factor is that the CSO carries out a census of agriculture from time to time and there are a couple of pieces of information which are worth noting. The most recent report which I can find on the CSO’s website is for 2010, so, four years old. The press release is here, on the CSO’s website and it summarises the findings nicely. The full report is here.

There are a couple of key pieces of information in the summary which matter here:

  • More than half of all farm holders were aged 55 years or more. The number of farmers aged under 35 fell by 53% since 2000
  • One in eight (12.4%) farms is owned by a female.

Additionally, it is possible that the vast majority of farmers are rural dwellers but a greater proportion of the population are now urban dwellers. I have not found straight figures for that.

These figures are not representative of the population as a whole. If you look at the CSO census figures, only a third of the population of the country is over the age of 45 which means the proportion of the population which is over the age of 55 is less again.

Additionally, in 2011, at the time of the last census, more than 50% of the population were female. You can find the CSO’s population statistics by age from 2011 here.

Both the headline and the first line of the story give the impression initially that the results are nationally representative but as the survey was of farmers, the participants are age and sex skewed away from the shape of the population as a whole.

So, the subheading mentioned farmers; what actually is the problem here?

Three things: we get our news from various sources which means that pieces of information might get cut, such as on a twitter feed which may not necessarily highlight that this is a Farming Spotlight piece. Not everyone might click through beyond the headline. This is particularly important as links get passed around. This by the way was the Examiner’s own tweet of its front page and inline, you will only see the top half.

Secondly, for me, a story which effectively boils down to “a sample of the population skewed by age, gender and urban/rural divide have this opinion which may or may not be representative of the population as a whole” really doesn’t belong as the top front headline on a national newspaper. In short, while it is, in passing, interesting, it isn’t really a major story.

Thirdly: the Irish Examiner has not provided any useful information (that I can find) in terms of the number of respondents, how the survey was carried out and what the estimated margin of error was. If you check any political poll reporting, the number of people surveyed along with the margin of error is always provided, along with an indication of when the poll was carried out. This is news at the moment, possibly because of the National Ploughing Championships but again, the statistical basis for the survey is missing.

 

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