An Analyst Is Assigned a Blind Quality Control Sample of Blood

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
The accepted true value of this sample is 24.7 ug/mL. What is the % error between the mean obtained by the analyst and the accepted true value? Report to two significant figures

A) 2.9
B) -2.9
C) 4.2
D) -4.2
E) None of the above