13. Your laboratory is evaluating the precision of a colorimetric method for creatinine in serum in which the sample is reacted with alkaline picrate to produce a color. Rather than perform one set of analyses, several sets with different samples are performed over several days, in order to get a better estimate of the precision of the method. From the following absorbance data, calculate the pooled standard deviation. Day 3 (Sample C) Day 1 (Sample A) Day 2 (Sample B) 0.826 0.682 0.751 0.810 0.655 0.702 0.880 0.661 0.699 0.865 0.724 Average: 0.845 0.666 0.719