The Concentration of Hexane (A Common Solvent) Was Measured in Units

question 21

Multiple Choice

The concentration of hexane (a common solvent) was measured in units of micrograms per liter for a simple random sample of thirteen specimens of untreated ground water taken near a municipal landfill. The sample mean was 424.2 with a sample standard deviation of 6.5. Fourteen specimens of treated ground water had an average hexane concentration of 246.0 with a standard deviation of 5.9. It is reasonable to assume that both samples come from populations that are approximately normal. Construct a 99% confidence interval for the reduction of hexane concentration after treatment.

• A)(175.6, 180.8)
• B)(175.1, 181.3)
• C)(176.7, 179.7)
• D)(170.9, 185.5)

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Definitions:

Cash Payback Period

The length of time required for an investment to generate cash flows sufficient to recover the initial cost of the investment.

Residual Value

The estimated salvage value or end-of-useful life value of an asset after all depreciation has been deducted.

Net Cash Flow

The amount of cash generated or used by a company in a specific period, calculated as cash received minus cash spent.

Operating Income

Profit realized from a business's core operations, excluding deductions of interest and taxes.