296 Final Exam With Verified Solutions

is the sample size large enough so that the sample proportions follow a normal distribution? n=40 p=0.25 {Ans: yes}*United Flights in December* We look at a random sample of 1000 United flights in the month of December comparing the actual arrival time to the scheduled arrival time. Computer output of the descriptive statistics for the difference in actual and expected arrival time of these 1000 flights are shown below. N, Mean, StDev, SE, Mean, Min, Q1, Median, Q3, Max 1000, 9.72, 41.9, 1.32,-42, -12, 0, 19, 471 {Ans: 1.) What is the sample mean difference in actual and expected arrival times? What is the standard deviation of the differences? x-bar= 9.72 s=41.9 2.) Based on the computer output, is it safe to assume this sample is normally distributed? no 3.) Can we proceed using the t distribution to build a confidence interval for this mean? yes 4.) The 95% confidence interval is: 7.12 to 12.3}Test H0 : μT=μC vs Ha : μT<μC using the fact that the treatment group (T) has a sample mean of 8.6 with a standard deviation of 4.1 while the control group (C) has a sample mean of 11.2 with a standard deviation of