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

question 22

Multiple Choice

The concentration of hexane (a common solvent) was measured in units of micrograms per liter for a simple random sample of twelve specimens of untreated ground water taken near a municipal Landfill. The sample mean was 720.2 with a sample standard deviation of 8.8. Eleven specimens of Treated ground water had an average hexane concentration of 695.1 with a standard deviation of 9.1.
It is reasonable to assume that both samples come from populations that are approximately normal. Construct A 90% confidence interval for the reduction of hexane concentration after treatment.

• A) (23.6, 26.6)
• B) (18.3, 31.9)
• C) (21.8, 28.4)
• D) (22.2, 28.0)

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Definitions:

Test Statistic

A value computed from sample data to decide whether to reject the null hypothesis in hypothesis testing.

Red Blood Cell Counts

A measurement of the number of red blood cells per unit volume of blood, used to assess overall health and diagnose various medical conditions.

Confidence Interval

A range of values, derived from sample statistics, that is likely to contain the value of an unknown population parameter, with a given level of confidence.

Ethanol

A volatile, flammable, colorless liquid commonly used as a fuel and in chemical synthesis, and also found in alcoholic beverages.