Measurements of groundwater concentrations of silica (SiO2) in mg/L, were made at a sample of 12 wells in Birmingham. The sample mean concentration was 61.3 and the standard deviation was 5.2.
(a) Can you conclude that the mean concentration of silica is greater than 60 mg/L?
(b) Can you conclude that the mean concentration of silica is less than 65 mg/L?