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Day: October 21, 2021

In using your validated regression equation to predict ozone concentration for specified values of the X variables and considering that ozone had to be log-transformed in order to compute the linear regression, how would your prediction be affected by transformation bias?

October 21, 2021

nonlinear regression is not affected by outliers.

October 21, 2021

For the soil arsenic data described in Example 19.2 of Section 19.4.1, use the approximate sample size formula of Equation 19.2 in that section to compute the recommendedminimum data sample size for (A)two-sided 99% confidenceinterval on the population mean arsenic concentration; and (B) one-sided 99% upper confidence limit. (C) Obtain the recommended sample size for this analysis using ProUCL’s Number of Samples -> Estimate Mean menu. Compare and comment on the results. (D) These computations assumethatthe datato be collected will be normally distributed and free of outliers.What are the sample sizes if the data are not normally distributed, as is more likely than not to be the case? Hint: Try using VSP. (E) After collecting the samples, what steps should be taken to verify the adequacy of the sample size?

October 21, 2021

Groundwater sampling is to be performed for a groundwater contaminant, and there is no basis for assuming that the data to be collected will be normally distributed and free of outliers. The Action Level or AL for the contaminant is 300 μg/l, and we may tentatively assume 10% of the AL, that is, 30 μg/l as the width of the gray region. Based on historical sampling data for the contaminant, the standard deviation may be assumed as 50 μg/l. The Type I (i.e., α) and Type II (i.e., β) error rates may be assumed as 0.05 and 0.10, respectively. (A) Use the appropriate procedure in ProUCL’s Number of Samples menu to compute the recommended minimum data sample size for comparing the contaminant concentrations with the AL; (B) Use the appropriate ProUCL procedure to compute the recommended minimum data sample size for comparing the site contaminant concentrations with the background concentrations; (C) If the computed sample sizes are not feasible in terms of the available budget, what options are available for sample size reductions? (D) How should the adequacy of the computed sample sizes be verified?

October 21, 2021

The main purpose of background sampling is to compare constituent concentrations between areas affected and unaffected by site activities

October 21, 2021

Overall, would you characterize the copper at this site as a contaminant of potential concern?

October 21, 2021

The primary purpose of risk assessment is to limit chemical exposure risks to humans and ecological communities

October 21, 2021