deviation of 2%. Calculate a 95% confidence interval for the population mean of students who took a support course. (Type numbers in Excel calculator without percent sign)
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- An auditor of the USPS wants to examine its special two day mail handling to determine the proportion of parcels that actually arrive within the promised two day period. A randomly selected sample of 1600 such parcels is found to contain 1250 that were delivered on time. The USPS claims that more than 75% of parcels are delivered on time. Does a 95% confidence interval support this claim?An auditor of the USPS wants to examine its special two day mail handling to determine the proportion of parcels that actually arrive within the promised two day period. A randomly selected sample of 1600 such parcels is found to contain 1250 that were delivered on time. Use this to construct a 95% confidence interval for the parcels delivered on time.A 90 percent confidence interval is to be created to estimate the proportion of television viewers in a certain areawho favor moving the broadcast of the late weeknight news to an hour earlier than it is currently. Initially, theconfidence interval will be created using a simple random sample of 9,000 viewers in the area. Assuming that thesample proportion does not change, what would be the relationship between the width of the original confidenceinterval and the width of a second 90 percent confidence interval that is created based on a sample of only 1,000viewers in the area?(A) The second confidence interval would be 9 times as wide as the original confidence interval.(B) The second confidence interval would be 3 times as wide as the original confidence interval.(C) The width of the second confidence interval would be equal to the width of the original confidence interval.(D) The second confidence interval would be 1/3 as wide as the original confidence interval.(E) The second…
- The production manager in an automobile plant is concerned with the number of cars that do not pass the final quality control inspection. In the last two hours he noted that in a sample of 120 cars only 92 were acceptable. The lower and upper limit of a 95% confidence interval for the true percentage of all cars that would not pass the final quality control inspection would be:A student who is studying to become a computer scientist would like to estimate the proportion of Android users at his university because he would like to begin offering an Android repair service to students to support himself financially. He randomly samples 31 students and asks them if they own an Android phone to which 13 say they do. Fill in the blanks below to construct a 95% confidence interval for the proportion of students at his university who own a Android phone. Round the point estimate and standard error to four decimal places. Report the critical value to two decimal places. Note that the critical value should be reported immediately after the ±. _____________ ± ___________ * ______________It is believed that the more carry-on baggage passengers have, the longer it takes the airplane to unload and load passengers. A regional airline considers a new policy of allowing only one carry-on baggage per passenger. Before doing so, the airline collected a sample of 900 passengers, out of whom, 360 had more than one bag. Develop a 95% confidence interval for the proportion of the travelling population that would have been impacted had the one-bag limit been in effect. What is the value of the lower limit of the confidence interval? Round your answer to two decimal places.
- Adults are spending more and more time on the Internet, and the number experiencing computer-based or Internet-based crime is rising. A 2018 Gallup Poll of 1019 adults, aged 18 and older, found that 723 of those in the sample said that they worry about having their personal, credit card, or financial information stolen by computer hackers. Although the samples in national polls are not SRSs, they are similar enough that our method gives approximately correct confidence intervals. Explain in words what the parameter p is in this setting ? Use the poll results to give a 95% confidence interval for p.The owner of a gasoline production company is planning to open another plant and surveyed engineers who he can hire for his new branch. At present, there are 45,118 engineers in his current plant. A sample of 13,602 is selected from the engineers and has received 7,009 feedbacks. Construct a confidence interval at 95% and calculate the margin of error at 98% confidence level.In August 2005, researchers for the American Society for Microbiology and the Soap and Detergent Association monitored the behavior of more than 6300 users of public restrooms. They observed people in public venues such as Turner Field in Atlanta and Grand Central Station in New York City. They found that 2393 of 3206 men washed their hands, compared to 2802 of 3130 women. For each gender, construct a 99% confidence interval for the population proportion who wash their hands in public restrooms. (4 decimals)
- A sky train has surveyed a simple random sample of air travelers to find out whether they would be interested in paying a higher fare in order to have access to wifi during their travel. Of the 100 travelers surveyed, 40 said wifi access would be worth a slight extra cost. Construct a 90% confidence interval for the population proportion of sky train travelers who are in favor of the wifi ideaTaking a random sample of 35 individuals waiting to be serviced by the teller, we find that the mean waiting time was 22.0 minutes and the standard deviation was 8.0 minutes. Construct a 97% confidence interval of the mean waiting time for all individuals waiting in the service line. If an individual waited for 15 minutes, would this be considered unusually fast?A researcher surveys 50 individuals in Smithville and 40 in Amherst, finding that 30% of smithville residents moved last year, while only 22% of Amherst residents did. Is there enough evidence to conclude that mobility rates in the two communities differ? Use a two-tailored alternative, and a=0.10. Again, find the p-value and a 90% confidence interval for the difference in proportions
