Nitrite (NO2) was measured by two methods in rainwater and unchlorinated drinking water. The results standard deviation (number of samples) are
Sample source Gas chromatography Spectrophotometry
Rain water 0.69 ± 0.005 mg/L(n = 7) 0.063 ± 0.008 mg/L (n = 5)
Drinking water 0.078 ± 0.007 mg/L (n = 5) 0.087 ± 0.008 mg/L (n = 5)
(a) Do the two methods agree with each other at the 95% confidence level for both rainwater and drinking water?
(b) For each method, does the drinking water contain significantly more nitrite than the rainwater (at the 95% confidence level)?