Groundwater Sampling Devices
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metals were analyzed by Inductively Coupled PlasmaMass Spectrometry (ICP
MS) according to SW 846 (US EPA 1994).
Statistical analyses
For each analyte in each study, paired t-tests (at 95% confidence level, α =
0.05) were performed on the replicate samples taken with all the devices except
the diffusion bag samplers. Because the tests with the diffusion bag samplers
were more of a batch study, simple (randomized) t-tests were performed on those
data sets. In all cases except for one, the data sets were found to be normally dis-
tributed (using a P value of 0.050), and thus did not require any transformation
or the use of non-parametric statistical analyses. The one exception was the com-
parison between the arsenic concentrations in the PDB sampler (all below the
detection limit) and the controls. That data set (using half the detection limit for
the values in the PDB sampler) was not normally distributed, so a Mann
Whitney Rank Sum test was performed.
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