“Some of our members wash cars less often than others!” says breakdown service

July 10th, 2012

From the Daily Mail, July 9th, 2012:

Wealthier motorists are ‘too posh to wash’ their cars, an AA survey reveals today.

They are more willing to drive dirtier vehicles for longer than poorer but prouder owners who prefer to keep their cars clean.

Only one in 17 car owners from professional and managerial backgrounds wash their vehicle once a week, reveals the survey. That compares with one in 12 among lower-income motorists, which includes manual and part-time workers.

Overall, a grubby 3 per cent of the 18,080 AA members surveyed admitted to washing their cars just once a year or not at all. Among women drivers, this figure doubled to 6 per cent.

While 18,080 represents a remarkably large sample size, it’s worth bearing in mind the self-selecting nature of the respondents – all of respondents were people who’d chosen to be members of the AA. This could throw up all sorts of biases – for example, the average higher-income driver may well be able to afford to be part of the AA, whereas the average lower-income driver may not.

In effect, this would bias the survey to include a higher proportion of those lower-income drivers who prioritise car care and thus fork out for AA cover, whereas the lower-income driver who doesn’t see car care as as much of a priority will be missing from the survey – a distinction which may be lessened where the drivers have more disposable income.

What’s more, the ensuing breakdown is little more than data-mining – without outlining ahead of time the questions you’re looking to answer (such as ‘do wealthier people neglect washing their cars?’), any findings from the data can’t be confidently stated, especially with the narrow margins involved.

Take for example the 1 in 17 wealthier-backgrounded people who wash their car each week, compared to the 1 in 12 people of lower-income: broken down to a percentage, this is the difference between 5% and 8% – which may not pass for statistically significant. It’s certainly not enough to assert that poorer people are ‘prouder’ of their cars.

Consider also – does the survey show that poorer people have cleaner cars, or that people of lower-income wash their own cars more often than those who have the disposable income to pay to have their car cleaned by someone else? Similarly, the statement ‘3% of people admitted to washing their cars just once a year’ may well show that there are unwashed cars around, or it may actually show the number of people who wouldn’t say they had ‘washed their car’ if someone else had washed it for them. Without access to the survey and the questions, we have data but no information.

The survey showed that drivers in Scotland and North-East England have the cleanest cars, with 11 per cent of owners washing them every week. This compares to just 4 per cent in London and South-West England.

Rather confusingly, here, the AA has changed its mind as to what the data represents – if the more well-off amongst us wash our own cars less often than the lower-income driver, would a higher incidence of car-washing in the North East show a higher proportion of cleaner cars, or a higher proportion of lower-income drivers? Again, we have data but no information.

AA president Edmund King said: ‘The Victorian concept of the ‘great unwashed’ perhaps needs to be reversed as richer drivers have dirtier motors.’

Before we go overturning any old adages, it’s probably best to analyse and understand what story we’ve uncovered. If we don’t we’re largely left with a case of Have Data, Will Mine.