User:Femke/crime against significant digits

This page in a nutshell: Do not use too many significant digits: the later digits often don't convey information. Sources may give too many significant digits, or give the appropriate context to justify giving more precision.

Within technical topics, the amount of digits in a number give a rough indication of precision. If I say I'm 1.7 m tall, I'm giving less information and precision than if I say I'm 1.68 m tall. But when I say I'm 1.68375867843 m, you know something fishy is going on.

Often, sources used for Wikipedia give many significant digits, and it's inappropriate to simply copy those numbers to Wikipedia for two reasons

some sources given inappropriate amount of significant digits themselves. One example from our Earth article is the mean global temperature, as reported by the BBC. That number was given in 5 significant digits, where we in reality have no idea about the last two digits. The error came from the BBC, who decided that the sum 14.(?) + 0.58 = 14.58.
more frequently, a source gives a very specific number. There are multiple definitions of unemployment, and a source will specify which definition they use. For Wikipedia it's sometimes not relevant which definition is used, and if we drop that information, we should also drop the precision.

Simple arithmetic can lead to errors in significant digits too

If your source says a (measured) variable B=1.1 among three people, division would give you 0.37, not 0.3666666.