Confidence interval for Cigarette Tar The mean tar content of a simple random sa
ID: 2957533 • Letter: C
Question
Confidence interval for Cigarette Tar The mean tar content of a simple random sample of 25 unfiltered king size operates is 21.1 mg, with a standard deviation of 3.3 mg. The mean tar content of a simple random sample of 25 filtered 100 mm cigarettes is 13.2 mg with a standard deviation of 3.7 mg (based on data from Data set 4 in appendix B). Construct a 90% confidence interval estimate of the difference between the mean tar content of unfiltered king of the cigarettes and the mean tar content of filtered 100 mm cigarettes. Does the result that 100 mm filtered cigarettes have less tar than unfiltered king size cigarettes? Hypothesis Test for Cigarette Tar Refer to the sample data in Exercise 11 and use a 0.05 significance level to rear the claim for that unfiltered king size cigarettes have a mean tar common greater than that of a filtered of 100 mm cigarettes. What does the result suggest about the effectiveness of cigarette falters? Hypothesis Test for Checks and Charges The author collected to a simple random sample of the cents portions from 100 checks from 100 credits card charges. The common portion of the checks has a mean of 23.8 cents and standard deviation of 32.0 cents. The cent portion of the credit charges have a mean of 47.6 cents and a standard deviation of 33.5 cents. Use a 0.05 significance level to test the claim that the cent portion of the check amounts have a mean that is less than the mean of the cents portion of the credit card charges. Give one reason for that might explain a difference.Explanation / Answer
When you do a 2-sided hypothesis test with significance level alpha, to find the critical value, you have to split alpha between the two tails of the z- or t-distribution. So if alpha = 0.05, then to find the critical value z* or t*, you need to take 0.05/2 = 0.025 and look up the critical value that corresponds to 0.025.