How to abuse statistics (again)
Every so often I find misused or misinterpreted statistics which are so flagrant that they are worth sharing with others. Here goes with another two.
(1) The news item read:
For years gardeners have been told that tea bags were perfect material for the compost heap, but there is new evidence for consumers that they at least need to rip the bags open before they throw them on the heap. Updated research last autumn has found that six out of the seven largest tea bag manufacturers do not make fully compostable bags. Between 20 percent and 30 per cent of the bags are made of polypropylene, a type of plastic used to glue the sides of the bag together.
So, are you clear? Does that mean that a quarter of all bags are made of polypropylene? Or a quarter of each bag is, with the plastic on the sides of the bag? How do the figures "between 20 per cent and 30 per cent" tie in with the statistics of the largest bag makers?
The saga doesn't end there. A photo of used tea bags accompanied the article, captioned - wait for it - "Six out of seven tea bags are not compostable". D'OH!
(2) Another news item:
The average holidaymaker jets off with a case full of more than £3000-worth of tech, toiletries and clothes. According to research from My Nametags, the typical suitcase alone will leave a £141.00 dent in the bank balance. On top of that, sunglasses, hair straighteners, shoes and trainers add £413.66 to the bill, with the rest of the £3000 made up from clothes and technology such as laptops.
Just note - the average suitcase is not £140.99, not £141.01, but exactly £141.00; and the accessories are £413.66, not £413.65 or £413.67. I can't remember how much I paid the last time that I bought a suitcase, and I imagine that this is true for the majority of people - and also for the items inside. So the figures are plucked out of the air and given an aura of authority.
Conclusion: Journalists should be literate - and numerate
(1) The news item read:
For years gardeners have been told that tea bags were perfect material for the compost heap, but there is new evidence for consumers that they at least need to rip the bags open before they throw them on the heap. Updated research last autumn has found that six out of the seven largest tea bag manufacturers do not make fully compostable bags. Between 20 percent and 30 per cent of the bags are made of polypropylene, a type of plastic used to glue the sides of the bag together.
So, are you clear? Does that mean that a quarter of all bags are made of polypropylene? Or a quarter of each bag is, with the plastic on the sides of the bag? How do the figures "between 20 per cent and 30 per cent" tie in with the statistics of the largest bag makers?
The saga doesn't end there. A photo of used tea bags accompanied the article, captioned - wait for it - "Six out of seven tea bags are not compostable". D'OH!
(2) Another news item:
The average holidaymaker jets off with a case full of more than £3000-worth of tech, toiletries and clothes. According to research from My Nametags, the typical suitcase alone will leave a £141.00 dent in the bank balance. On top of that, sunglasses, hair straighteners, shoes and trainers add £413.66 to the bill, with the rest of the £3000 made up from clothes and technology such as laptops.
Just note - the average suitcase is not £140.99, not £141.01, but exactly £141.00; and the accessories are £413.66, not £413.65 or £413.67. I can't remember how much I paid the last time that I bought a suitcase, and I imagine that this is true for the majority of people - and also for the items inside. So the figures are plucked out of the air and given an aura of authority.
Conclusion: Journalists should be literate - and numerate
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