Week_6_Math_225n_Statistics_Quiz With Answers

Question 1 A statistics professor recently graded final exams for students in her introductory statistics course. In a review of her grading, she found the mean score out of 100 points was a x ̄=77 , with a margin of error of 10. Construct a confidence interval for the mean score (out of 100 points) on the final exam. That is correct! Answer: (67, 87) Question 2 A random sample of adults were asked whether they prefer reading an e-book over a printed book. The survey resulted in a sample proportion of p ′ =0.14 , with a sampling standard deviation of σ p ′ =0.02 , who preferred reading an e-book. Use the empirical rule to construct a 95% confidence interval for the true proportion of adults who prefer e- books. That is correct! Answer: ( 0.10, 0.18) Question 3 The pages per book in a library are normally distributed with an unknown population mean. A random sample of books is taken and results in a 95% confidence interval of (237,293) pages. What is the correct interpretation of the 95% confidence interval? That is correct! We estimate with 95% confidence that the sample mean is between 237 and 293 pages. We estimate that 95% of the time a book is selected, there will be between 237 and 293 pages. We estimate with 95% confidence that the true population mean is between 237 and 293 pages. Question 4The population standard deviation for the heights of dogs, in inches, in a city is 3.7 inches. If we want to be 95% confident that the sample mean is within 2 inches of the true population mean, what is the minimum sample size that can be taken? Round up to the nearest integer. That is correct! Answer: 14 dog heights Question 5 Clarence wants to estimate the percentage of students who live more than three miles from the school. He wants to create a 98% confidence interval which has an error bound of at most 4% . How many students should be polled to create the confidence interval? z 0.10 z 0.05 z 0.02 z 0.01 z 0.005 5 1.28 1.64 1.96 2.32 2.57 2 5 0 6 6 Use the table of values above. That is correct! Answer: 846 Students Question 6 The average score of a random sample of 87 senior business majors at a university who took a certain standardized test follows a normal distribution with a standard deviation of 28 . Use Excel to determine a 90% confidence interval for the mean of the population. Round your answers to two decimal places and use ascending order.. Score 516 536 462 461 519 496 517 488 521 HelpCopy to ClipboardDownload CSV That is correct! Answer: (509.30, 519.18)Question 7 A random sample of 28 statistics tutorials was selected from the past 5 years and the percentage of students absent from each one recorded. The results are given below. Assume the percentages of students' absences are approximately normally distributed. Use Excel to estimate the mean percentage of absences per tutorial over the past 5 years with 90% confidence. Round your answers to two decimal places and use increasing order. Number of Absences 13.9 16.4 12.3 13.2 8.4 4.4 10.3 8.8 4.8 HelpCopy to ClipboardDownload CSV