A tobacco company claims that its best-selling cigarettes contain at most 40 mg of nicotine. This claim is tested at the 1% significance level by using the results of 15 randomly selected cigarettes.
The mean is 42.6 mg and the standard deviation is 3.7 mg. Evidence suggests that nicotine is normally distributed. Information from a computer output of the hypothesis test is listed.
Sample mean = 42.6 P-value = 0.008 Sample standard deviation = 3.7 Significance level = 0.01 Sample size = 15 Test statistic t = 2.72155 Degrees of freedom = 14 Critical value t = 2.62449 1. What are the degrees of freedom?
2. Is this a z or t test?
3. Is this a comparison of one or two samples?
4. Is this a right-tailed, left-tailed, or two-tailed test?
5. From observing the P-value, what would you conclude?
6. By comparing the test statistic to the critical value, what would you conclude?
7. Is there a conflict in this output? Explain.
8. What has been proved in this study?