Medicine: the pH of an arterial blood gas (ABG) sample is typically given out to 4 digits. 7.380 is about normal. 7.211 might seem about the same as 7.219, but

Medicine: the pH of an arterial blood gas (ABG) sample is typically given out to 4 digits. 7.380 is about normal. 7.211 might seem about the same as 7.219, but if one sample is 7.211 and 15 minutes later it's 7.219, you're doing something right. If it's 7.219 and in 15 minutes it goes down to 7.211, something is very wrong. Machine shops and engineering: every machinist makes every cut to, at a minimum, the nearest thousandth of an inch, and often to the tenths of thousandths; often over several inches (like piston heads and cylinders) This is what slip-clutch micrometers are for. A red optical filter for a physics experiment could easily be accurate to 720 nanometers with a band pass of 719.998 to 720.003 +/- 2 in the next digit. There are lots of examples in physics, go get a physics supply catalog.