Posted by Alyssa on .
Say you made three different mass measurements of a sugar cube. You know the mass is 1.0g. how would you know whether or not the measurements were accurate? Precise?

chemistry 
DrBob222,
Suppose you weighed the cube and obtained the following:
0.50 g; 1.0 g; 1.50 g
The average is 1.00 g; therefore, the accuracy is very good but the precision is lousy.
Suppose you weighed the cube and obtained the following:
0.50 g; 0.51 g; 0.49 g.
The average is 0.50 g which is far from the actual value of 1.0 g; therefore, the accuracy is lousy but the precision is good.
Suppose the weighings were as follows:
0.50 g; 0.60 g; 0.70 g.
The accuracy is not good (its a long way to 1.0 g) AND the precision is not good either.
The fourth case is the last possibility.
0.99 g; 1.0 g; 1.1 g.
The average is 1.0 g; therefore, the accuracy is very good and the precision is very good.