The article “Influence of Penetration Rate on Penetrometer Resistance” (G. Gagnon and J. Doubrough, Canadian Journal of Civil Engineering, 2011:741–750) describes a study in which twenty 2-L specimens of water were drawn from a public works building in Bridgewater, Nova Scotia. The mean lead concentration was 6.7μg/L with a standard deviation of 3.9μg/L.

a. The Health Canada guideline states that the concentration should be less than 10μg/L. Can you conclude that the water in this system meets the guideline?

b. A stricter guideline is being considered, which would require the concentration to be less than 7.5μg/L. Can you conclude that the water in this system meets this guideline?