Statistics for Environmental Engineers

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18.2 Lead Measurements. Below are measurements of lead in solutions that are identical except for the amount of lead that has been added. Fourteen specimens had an addition of 1.25 [g/L and 14 had an addition of 2.5 [g/ L. Is the difference in the measured values consistent with the known difference of 1.25 [g/ L?


Addition = 1.25 [g/L    1.1    2.0    1.3    1.0    1.1    0.8    0.8    0.9    0.8    1.6    1.1    1.2    1.3    1.2


Addition = 2.5 [g/L    2.8    3.5    2.3    2.7    2.3    3.1    2.5    2.5    2.5    2.7    2.5    2.5    2.6    2.7


18.3 Bacterial Densities. The data below are the natural logarithms of bacterial counts as measured by two analysts on identical aliquots of river water. Are the analysts getting the same result?


Analyst A    1.60    1.74    1.72    1.85    1.76    1.72    1.78


Analyst B    1.72    1.75    1.55    1.67    2.05    1.51    1.70


18.4    Highway TPH Contamination. Use a f-test analysis of the data in Exercise 3.6 to compare the TPH concentrations on the eastbound and westbound lanes of the highway.


18.5    Water Quality. A small lake is fed by streams from a watershed that has a high density of commercial land use, and a watershed that is mainly residential. The historical data below were collected at random intervals over a period of four years. Are the chloride and alkalinity of the two streams different?


Commercial Land Use


Residential Land Use


Chloride


Alkalinity


Chloride


Alkalinity


(mg/L)


(mg / L)


(mg/L)


(mg/L)


140


49


120


40


135


45


114


38


130


28


142


38


132


40


100


45


135


38


100

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