Massaging the figures

Dot writes: I was just trying to find out what percentage of gift cards don’t get redeemed, using everybody’s favourite research tool, Google. It was a silly question, come to think of it: did I mean “what percentage of cards don’t get fully redeemed?”, or “what percentage of money spent on gift cards is never turned back into goods?”, or “what percentage of people who have gift cards don’t redeem them?” Not that I found out a definitive answer to any of these questions – after all, there probably isn’t one – but I did note that headline writers can’t tell the difference between them: for example, this report based on US data from 2007, in which the heading mentions “27% of last year’s gift cards still unused” but the text says that “56 percent of respondents received gift cards and nearly a year later, 27 percent of gift card recipients have not used one or more of these cards”. Which is not the same thing at all.

Talking of such vaguely bandied statistics, one that fills me with scepticism is the assertion that if you stop on the hard shoulder of a motorway you have on average 20 minutes before something collides with you. When we were driving back from the English end of our Welsh holiday in July, we took a break at a service station on the M6 and Ken and Hugh were treated to a tour of a fire engine, which was parked there for purposes of Raising Awareness; the firemen were telling people about the twenty minute crash-free window. I can’t help wondering how the figure was obtained. Did somebody do an experiment sending people out to park on hard shoulders and then crouch in the bushes with a stop-watch? It seems more likely that, when cars parked on the hard-shoulder were then involved in a collision, the drivers were asked how long they had been there. But if that is the case the statistic should be “cars involved in collisions when parked on the hard shoulder had on average been there for twenty minutes”; and it doesn’t mean anything for your chances of being in such a collision in the first place. [That said, I wouldn’t want to hang about on the hard shoulder. Here’s a blog to instill a proper mood of caution.]

Ken got me a gift voucher for my birthday. Whatever the true numbers of unredeemed vouchers may be, I didn’t want to waste mine; so yesterday I went to the beauty parlour round the corner and had a 60 minute massage. It was wonderful. I’ve been ill on and off for the past three weeks now: the cough/cold/glandular thing I had over Frank’s birthday hadn’t wholly cleared up when I caught a variation on the same theme and started to get worse again, and I’m not over it yet. The massage wasn’t just pleasant at the time but made me feel astonishingly better for the rest of the day (admittedly with the additional help of paracetamol and sudafed). If I were just a teeny but richer I might make this a habit, but then it wouldn’t be such an astonishing treat. Now I just have to find time for a manicure and pedicure – for the gift voucher included those as well. I wonder, if you were having a massage with some firemen on the hard shoulder, how long on average it would be before you crashed?

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6 thoughts on “Massaging the figures

  1. Murray

    Dot – you are wasted in English, you would make a good statistician! When I hear a mean or percentage confidently proclaimed I think: now what kind of study would they have had to carry out to know that? And did they do it? And if they did how well?

    1. Dot

      Thankyou! I’m glad you approve. But it’s not really statistical skills I’m employing here, just critical thinking – and literary critics think critically too, at least some of the time!

      1. kenanddot

        I think Helen was referring to the last sentence of the post (which was, I’m afraid, just a cheap laugh stuck in there for the sake of a neat ending).

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