Removing a soil contaminant. A common hazardous compound found in contaminated soil is ben...

Removing a soil contaminant. A common hazardous compound found in contaminated soil is benzo(a)pyrene [B(a)p]. An experiment was conducted to determine the effectiveness of a method designed to remove B(a)p from soil (Journal of Hazardous Materials , June 1995). Three soil specimens contaminated with a known amount of B(a)p were treated with a toxin that inhibits microbial growth. After 95 days of incubation, the percentage of B(a) p removed from each soil specimen was measured. The experiment produced the following summary statistics:  and s = 1.5.

a. Use a 99% confidence interval to estimate the mean percentage of B(a)p removed from a soil specimen in which the toxin was used.

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b. Interpret the interval in terms of this application.

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c. What assumption is necessary to ensure the validity of this confidence interval?

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d. How many soil specimens must be sampled to estimate the mean percentage removed to within .5, using a 99% confidence interval?

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e. Find and interpret a 90% confidence interval for the true variance in the percentages of B(a)p removed.