A student carried out several different determinations of the density of the metal ruthenium. The students results were as follows:
Experiment 1 2 3 4 5 6
Density (g X cm-3) 12.68 12.34 12.21 12.10 12.18 12.38
If the true density is 12.30 g X cm-3, what is the percent error in the mean value?