Numeracy and Spurious Accuracy

While I’m not convinced by Rishi Sunak’s plan to improve British standards of numeracy, I wholly support the objective. I seem to be battling on a daily basis with statements which either make no sense if you inspect the numbers, or where the underlying message is confused by poor presentation.

One particular bête noir is “spurious accuracy”, where a number is quoted to a vast number of significant digits because “the computer said so”, without any thought about whether that makes any sense.

Here’s a direct quote from an email I received this morning from the Liberal Democrats:

We understand that our members may wish to move on to Monthly Direct Debit to make budgeting easier. As a result, we’re happy to be able to offer you the ability to split your payments down to £6.979166666666666 per month, should you wish.

That could scare some people as much as it helps them, no bank will support it, and it clearly demonstrates that the writer didn’t understand the subject. It should have been “£6.98 per month” (with a direct debit premium of 1p per year), or, even better, “£7 per month with an initial payment of £6.75”.

That said, being me I started thinking about whether I could make up the sum of £6.9791666 (recurring) in cash. It’s actually surprisingly easy and doesn’t involve farthings or groats (I’m not that old). £1 = 240d (old pre-decimal pennies). 1d therefore equals 0.0041666 (recurring). So the stated amount is £6.97 + 1/2p + 1d, and I am old enough to have 1/2p and 1d in my coin collection!

Now, will my bank accept a deposit of 1d?

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