A researcher wishes to estimate the average blood alcohol concentration for drivers involved in fatal accidents who are found to have positive BAC(blood alcohol concentration) values. He randomly selects records from 1100 such drivers in 2009 and determines the sample mean BAC to be 0.15 g/dL. with a standard deviation of 0.07 g/dL.

?(a) A histogram of blood alcohol concentrations in fatal accidents shows that BACs are highly skewed right. Explain why a large sample size is needed to construct a confidence interval for the mean BAC of fatal crashes with a positive BAC.

A. Since the distribution of blood alcohol concentrations is normally? distributed, the sample must be large so that the distribution of the sample mean will be approximately normal.

B. Since the distribution of blood alcohol concentrations is not normally distributed? (highly skewed? right), the sample must be large so that the distribution of the sample mean will be approximately normal.

C. Since the distribution of blood alcohol concentrations is normally? distributed, the sample mean will be approximately normal regardless of sample size.

D. Since the distribution of blood alcohol concentrations is not normally distributed? (highly skewed? right), the sample mean will be approximately normal regardless of sample size.

?(b) In? 2009, there were approximately? 25,000 fatal crashes in which the driver had a positive BAC. Explain why? this, along with the fact that the data were obtained using a simple random? sample, satisfies the requirements for constructing a confidence interval.

A. The sample size is greater than? 10% of the population.

B. The sample size is greater than? 5% of the population.

C. The sample size is less than? 10% of the population.

D. The sample size is less than? 5% of the population.

?(c) Determine and interpret a? 90% confidence interval for the mean BAC in fatal crashes in which the driver had a positive BAC.

The? 90% confidence interval for the mean BAC is? (Round to the nearest thousandth as? needed.)

Interpret a? 90% confidence interval for the mean BAC. Choose the correct answer below.

A. The researcher is? 10% confident that the population mean BAC is in the confidence interval for drivers involved in fatal accidents who have a positive BAC value.

B. There is a? 90% probability that the population mean BAC is in the confidence interval for drivers involved in fatal accidents who have a positive BAC value.

C. The researcher is? 90% confident that the population mean BAC is not in the confidence interval for drivers involved in fatal accidents who have a positive BAC value.

D. The researcher is? 90% confident that the population mean BAC is in the confidence interval for drivers involved in fatal accidents who have a positive BAC value.

?(d) All areas of the country use a BAC of 0.080 ?g/dL as the legal intoxication level. Is it possible that the mean BAC of all drivers involved in fatal accidents who are found to have positive BAC values is less than the legal intoxication? level?

A. No, it is not possible.

B. ?Yes, and it is highly probable.

C. Yes, but it is not likely.