Question

A researcher wishes to estimate the average blood alcohol concentration? (BAC) for drivers involved in fatal accidents who are found to have positive BAC values. He randomly selects records from 51 such drivers in 2009 and determines the sample mean BAC to be .16 g/dL with a standard deviation of 0.060 g/dL

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

?(Use ascending order. Round to three decimal places as? needed.)

A.

The lower bound is ____ and the upper bound is _____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.

B.The lower bound is ____ and the upper bound is _____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.

C. The lower bound is ____ and the upper bound is _____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) All areas of the country use a BAC of .10?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? Explain.

A. ?No, it is not possible that the mean BAC is less than

.1?g/dL, because it is possible that the true mean is not captured in the confidence interval.

B.

?Yes, it is possible that the mean BAC is less than

.1

?g/dL, because it is possible that the true mean is not captured in the confidence? interval, but it is not likely.

C.

?Yes, it is possible that the mean BAC is less than

0.1 ?g/dL, because it is possible that the true mean is not captured in the confidence interval and it is highly probable.

D.?No, it is not possible that the mean BAC is less than.1g/dL, because it is possible that the true mean is not captured in the confidence? interval, but it is not likel

Answer 1

The statistical software output for this problem is:

One sample T summary confidence interval:
? : Mean of population

90% confidence interval results:

Mean	Sample Mean	Std. Err.	DF	L. Limit	U. Limit
?	0.16	0.0084016805	50	0.14591958	0.17408042

Hence,

c) Option A; 0.146; 0.174

d) ?Yes, it is possible that the mean BAC is less than .1 ?g/dL, because it is possible that the true mean is not captured in the confidence? interval, but it is not likely.

Option B is correct.