72.8 (+-) 0.5 significant figures?

Question

(+-) the - is supposed to be below the +. I can't rememeber how to do significant figures! someone please help explain the rules again! thanks!

Answer 1

It's a bit long, but it's all explained here:

http://en.wikipedia.org/wiki/Significant...

In your case 72.8 +- 0.5 means that the value measured was 72.8 with a standard error of 0.5. That means that there is 68% probability that the "real" value lies between 72.3=72.8-0.5 and 73.3=72.8+0.5; 95% probability for it to lie in the domain 71.8 to 73.8.