Results of the analysis for the % Cu in an ore gave the following results: 70.35, 70.33, 70.24, 70.21, and 70.18. For the set, calculate

a) mean, standard deviation and the coefficient of variation,

b) Calculate the 95% confidence limits of the set. (t = 2.78 for 4 degrees of freedom at 95% confidence level.)

c) If the accepted value for the % Cu in the sample is 70.15, what is the relative error in parts per thousand?