A random sample of 15 employees was selected. The average age in the sample was 31 years with a variance of 49 years. Assuming ages are normally distributed, the 98% confidence interval for the population average age is

the variance in waiting times(in minutes) of 10 attendees at bethel woods, where attendees enter a single waiting line that feeds three checkpoint windows is 0.227 minutes. A 95% confidence interval for the population variance would be

You have obtained the number of years of education from one random sample of 38 police officers from City A and the number of years of education from a second random sample of 30 police officers from City B. The average years of education for the sample from City A is 15 years with a standard deviation of 2 years. The average years of education for the sample from City B is 14 years with a standard deviation of 2.5 years. Is there a statistically significant difference between the education levels of police officers in City A and City B?What is the appropriate test for this case? 2 sample z-testChi-square test     2-sample t-test2 sample paired t-test Carry out the test. The test statistic =   (round answer to two decimal places.)and the p-value is   (round answer to 2 decimal places)There     sufficient evidence at the 5% level to conclude that the education levels of police officers in City A and City B is significantly different.

A study has been made to compare the nicotine contents of two brands of cigarettes. Ten cigarettes of Brand A had an average nicotine content of 4.3 milligrams with a standard deviation of 0.6 milligram. Eight cigarettes of Brand B had an average nicotine content of 3 milligrams with a standard deviation of 0.4 milligram. Assume that the two sets of data are independent random samples from normal populations with equal variances. Answer the following, and round off your answer to three decimal places. (a) Find a pooled estimate of the population standard deviation. (b) Construct a 95% confidence interval for the difference between the mean nicotine contents of the two brands of cigarettes. (☐☐)