Blustery, with showers

Geoffrey Pullum, over at Language Log makes a point that also occurred to me many years ago when I first visited America and found myself watching a television weather forecast. The forecast was remarkable because it managed the trick of being simultaneously both extremely precise and totally meaningless. They said, if memory serves, "There is an eighty per cent chance of rain at three O'clock this afternoon."
It's marvellous. It's the curse of specious precision that afflicts so much of modern day life. I found myself sitting watching this forecast and asking myself the question, "If it doesn't rain at three O'clock, will they have been right or wrong?"
Actually you could ask the same question if it did rain. (And it did!)
There's another example on a poster at my Metro stop. At the bottom of the stairs is a poster that says "Regular use of the stairs can help you to avoid weight gain", a laudable sentiment certainly.

At the top another poster says "Congratulations. You have just used one sixteenth of the calories needed to avoid weight gain." The linguistic logic of that sentence may be a bit suspect (you need calories to avoid weight gain?) but the intent is clear. One sixteenth, eh? Not one fifteenth or one seventeenth but one sixteenth. And that regardless of your size, age, gender, level of fitness or whatever. Now that I think of it, it also doesn't specify a time frame - the calories I need in a week? A day? An hour? Speciously accurate and utterly meaningless.
I may come up with more, similarly nonsensical, examples later. Please feel free to add any that you can think of in the comments.