Assignment 3a

Assignment 3a - Assignment 3 (after C. Zhang 2007): 1. Soil...

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Assignment 3 (after C. Zhang 2007): 1. Soil samples were collected at two areas surrounding an abandoned mine and analyzed for lead. At each area several samples were taken. The soil was extracted with acid, and the extract was analyzed using flame atomic adsorption spectrometry. In area A, Pb concentrations were 1.2, 1.0, 0.9, 1.4 mg/kg. In area B, Pb concentrations were 0.7, 1.0, 0.5, 0.6, 0.4 mg/kg. a) Are these the Pb concentrations in the two areas significantly different from each other at 90% confidence level? 2. Samples of bird eggs were analyzed for DDT residues. The samples were collected from two different habitats. The data reported are: Sample collection area Number of samples Mean concentration (ppb) Standard Deviation (s) Area 1 4 1.2 0.33 Area 2 6 1.8 0.12 a) Are the two habitats significantly different (alpha=5%) from each other in the amount of DDT these birds to which were exposed. b) Calculate the 90% CI for DDT concentration in both areas c) If concentration of DDT in Area 2 can be assumed to have a normal distribution
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Assignment 3a - Assignment 3 (after C. Zhang 2007): 1. Soil...

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