Significant figures

[Marlene S]

I find the convention to display a fixed number of “significant figures” (e.g, 2 — 2.02 0r 2.2 or 2.000002) very strange – for me it goes against what I have learned in other classes about false precision (https://en.wikipedia.org/wiki/False_precision) and rounding.

What puzzles me most is: how can I possibly display the value 1.3968 with 2 decimal places with this method? (This is not me being nit-picky, this is an actual value for my report). If I just cut off 2 digits, it’s false rounding, but if I round from the 3rd decimal, I get 1.4000000… so I technically need to display an infinite number of zeros? (Obviously not, but is there a way I can round up reasonably and still not seem like I missed the point about significant figures?)

[Simon]

Don’t think in terms of decimal places, but in terms of significant figures.

1.3968 written to 3 significant figures would be 1.40

[Marlene S]

Ok thank you. I thought 0 does not count as significant figure…

[Simon]

Check your understanding with some quizzes:

How many significant figures do these numbers have?

Rounding to the specified number of significant figures

[Author]

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