Calculating Percentage Error: What to Do and How to Do It

[Kandy]

I forgot how to do percentage error, actually I kind of forgot what it is. I do remember multiplying somthg by 100% but i can't remember what i divide b4 that.

 

[Atomos]

In terms of percent error with regards to an accepted value:
Suppose you measured the atomic molar mass of lithium to be 8 g/mol. The accepted value is 6.94. You take the difference, which is 1.06g/mol, and the percent error is therefore +15.27% ie. 1.06/6.94 * 100%

 

[HallsofIvy]

Theoretically, you divide the error by the true value. In practice, you have an error because you don't know the true value! In that case you divide the (estimated error) by the measured value.