Significant Figures

With a title like that I suppose you are expecting a discussion about great artists or perhaps about magnificent sculptures. Sorry, but ‘significant figures’ in this case is the mathematical term.

You may be aware that in a previous life (before retirement) I was a science and physics teacher. One of the things I had to get across was the importance of significant figures. 3 g is not the same as 3.0 g. 3 g, which is to one significant figures, means that the item has a mass between 2.5 g and 3.5 g (OK, 3.499 repeating if you was to be pedantic!). 3.0 g, which is to two significant figures, means the mass has been measured more accurately and is between 2.95 g and 3.05 g.

What has this got to do with art? I thought this blog was ‘random ramblings about art! Well, the above is why I had a laugh this afternoon when I read’s email post from yesterday. I’d previously read that Sotheby’s were selling a painting by one of my favourite Dutch masters, Jan Steen.

Sotheby’s catalogue estimates the painting, “The Prayer Before the Meal”, to sell for “£5,000,000 to £7,000,000” (that is to one significant figure, if you are following the maths bit). However, the report of the painting being shown in Hong Kong prior to its sale in London had to convert, for some reason, from sterling to US dollars. Now, “the work is estimated at US$ 7,977,037.52 to US$11,167,852.53” (that’s ten SFs!)


A mathematician, a physicist and a civil engineer were asked “What is two plus two?”

“Exactly four,” said the mathematician.

“Between three and five,”said the physicist, (see the SF argument above) .

“Probably four, but we’ll call it ten to be on the safe side,” replied the civil engineer.


About notes to the milkman

I'm a printmaker based in the North West of England, living in Bolton and printing at Hot Bed Press in Salford. Please visit my website
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One Response to Significant Figures

  1. ms6282 says:

    Good post John. I find that getting across the importance of understanding how quoting results to too many sig figs gives a false impression of their accuracy, can be very difficult.

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