Arsenic is a known carcinogen and poison. The standard laboratory procedures for measuring arsenic concentration

(mg/L) in water are expensive. Consider the accompanying summary data and Minitab output for comparing a laboratory method to a new relatively quick and inexpensive field method (from the article “Evaluation of a New Field Measurement Method for Arsenic in Drinking Water Samples,” J. of Envir. Engr., 2008: 382–388).

Two-Sample T-Test and CI Sample N Mean StDev SE Mean 1 3 19.70 1.10 0.64 2 3 10.90 0.60 0.35 Estimate for difference: 8.800 95% CI for difference: (6.498, 11.102)

What conclusion do you draw about the two methods, and why? Interpret the given confidence interval. [Note: One of the article’s authors indicated in private communication that they were unsure why the two methods disagreed.]