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QUESTION 1 4 points In order to estimate the mean time students spend on their homework each night, a professor randomly selects 25 students and finds the standard deviation of this sample to be 0.5 hours. The confidence interval for the mean amount of time spend studying each night for all students is (1.751, 2.249). Assuming the time spent by students is normally distributed, which confidence level the professor used to construct the confidence interval? QUESTION 2 4 points The manager of a paint store, wants to estimate the mean amount of a product sold per day. He selected a sample of 25 business days and found a sample mean of 30 litres and a sample standard deviation of 10. Assuming that the daily amounts are normally distributed, construct a 90% confidence interval for the mean amount of the product sold per day. (26.584 , 33.416) O (26.578 , 33.422) (26.71, 33.29) (27.872 , 36.128) QUESTION 3 4 points Save The manager of a restaurant wants to estimate the average time customers spent in the restaurant. Assume that the standard deviation of the population is known to be 15 minutes. The manager would like to construct a 95% confidence interval for the average time customers spent in the restaurant. Find the appropriate sample size necessary to achieve a margin of error of 4.9 minutes. Click Save and Submit to save and submit. Click Save All Answers to save all answers. Save All Answers Save and Su G Search or type URLQUESTION 4 4 points Save Ans State the null and the alternative hypotheses for the following situation: It is claimed that the mean age of Zayed University students is more than 22 years. O Ho: H2 22 versus H1: H 22 O Ho: H 22 QUESTION 5 4 points Save Answ A random sample of 30 laptops has a mean price of 1000 AED and a standard deviation of 140 AED. Find a point estimate for the mean price of all laptops. QUESTION 6 4 points Save Answer The students affairs committee at ZU claims that the average time it takes students to reach the university during the morning rush hours exceeds 25 minutes. Based on a random sample of 30 students, a MTH 213 student performed the appropriate test and confirmed the committee's claim. What type of error could be made in this case? O Type II error Not enough information Type I error 4 points Save Answer QUESTION 7 What happens to the width of a confidence interval as the level of confidence decreases? The width of the confidence interval decreases The width of the confidence interval increases The width of the confidence interval will not change Click Save and Submit to save and submit. Click Save All Answers to save all answers. Save All Answers Save and SubmitQUESTION 8 An automobile manufacturer substitutes a different engine in cars that were known to have an average miles-per-gallon rating of 30 on the highway. The manufacturer wants to test whether the new engine changes the miles-per-gallon rating of the automobile model. A random sample of 16 trial runs gives a sample mean of 33.4375 miles per gallon and a sample standard deviation of 5.5 miles per gallon. Assuming normality of miles-per-gallon ratings and using the 0.05 level of significance, is the average miles-per-gallon rating on the highway for cars using the new engine different from the rating for cars using the old engine? O Ho: H = 30 vs H1: H = 30 P- value = 0.025 reject Ho O Ho: H = 30 vs H1: H = 30 P- value = 0.012 reject Ho O Ho: H =30 vs H1: H =30 P-value = 0.024 reject Ho O Ho: H = 30 v5 Hi: H = 30 P- value = 0.025 do not reject Ho QUESTION 9 4 P A researcher computed 88%, 92% and 96% confidence intervals for a population mean. Assume that the sample mean is 200, Below are the three confidence intervals along with another confidence interval constructed based on a different sample, which interval is the 92% confidence interval? (197.83 , 202.17) (198.18 , 201.82) (198.39 , 201.61) (197.80, 201.44) 4 pol QUESTION 10 Click Save and Submit to save and submit. Click Save All Answers to save all answers.QUESTION 10 4 points The HR manager of an organization is bargaining to get a new dental insurance plan. He claims that the yearly family dental expenses of its employees does not exceed 20000 AED. A random sample of 10 employees reveals that the average family dental expenses is 20500 and the standard deviation is 900 AED. Assuming normality of the yearly family dental expenses, at which significance level of you will contradict the manager's claim? O 38 O Ho: US38 versus H1: H > 38 QUESTION 15 A manufacturer of golf balls claims that the company controls the weights of the golf balls accurately so that the average of the weights is not more than 45 g. A random sample of 36 golf balls yields a sample mean of 46 g and a sample standard deviation of 4 g. Find the P-value of the test. Round your answer to three decimal places. QUESTION 16 It was claimed that the average speed of cars traveling on a section of Al Khaleej Al Arabi is more than 115 km/h. We test the hypothesis Ho:# $ 115 versus Hu >115. The null hypothesis is rejected. Describe the type I error in the context of the problem. Conclude that the average speed of cars traveling on a section of Al Khaleej Al Arabi is at most 1 15 km/h when in fact it exceeds 115 km/h. Conclude that the average speed of cars traveling on a section of Al Khaleej Al Arabi is more than 115 km/h when in fact it exceeds 115 km/h. Conclude that the average speed of cars traveling on a section of Al Khaleej Al Arabi is at most 115 km/h when in fact it does not exceed 115 km/h. Conclude that the average speed of cars traveling on a section of Al Khaleej Al Arabi is more than 1 15 km/h when in fact it does not exceed 115 km/h. Click Save and Submit to save and submit. Click Save All Answers to save all answers. Save All ArrawersQUESTION 17 A sample of 36 seven-year-old girls had a sample mean weight of 42 pounds and a sample standard deviation of 4.8 pounds. Determine a 90% confidence interval for the mean weight of the seven- year-old girls. (40.684 , 43.316) (40.648 , 43.352) (44.02 , 45.98) (44.008 , 45.992) QUESTION 18 An agency responsible for electricity distribution would like to estimate the average electric bills for a particular month for single-family homes in a large city. Based on a recent study, the sample mean is 1200 AED. Below are two confidence intervals constructed using the normal distribution and the t-distribution. The third one was calculated from on a different sample, Which interval was constructed using the t-distribution? (1050, 1250) (1120, 1280) (1100, 1300) QUESTION 19 An automatic bottling machine fills oil into 2-liter (2,000 ml) bottles. A random sample of 25 bottles coming out of the machine was selected and the exact contents of the selected bottles are recorded. The sample mean was 1995 ml. The population standard deviation is known from past experience to be 10 ml. Use a significance level a = 1% to test if the average amount filled by the machine into a bottle is at least 2,000 ml. O Ho: H 2 2000 vs H1: H 2000 P-value = 0.994 do not reject Ho Click Save and Submit to save and submit, Click Save All Answers to save all answers. Save All AnswerQUESTION 20 4 points Save A A statistics professor has office hours from 9:00 A.M. to 10:30 A.M. daily. A sample of waiting times to meet with the professor (in minutes) is given below 22 20 14 25 34 30 28 28 28 19 22 25 25 10 32 17 22 19 22 25 24 15 18 16 We want to test if the population mean is at least 20 minutes. Assuming that the waiting times are normally distributed, calculate the test statistic. Round your answer to two decimal places. O z=0.35 O z = 1.53 O t= 0.35 Of = 1.53 QUESTION 21 4 points Save A A test of Ho: u = 50 versus HI: H # 50 is performed using a significance level of 0.01. The P-value is 0.015. If the true value of u is 55, does the conclusion result in a Type I error, a Type II error or a correct decision? Type I error O Type II error Correct decision Not enough information 4 points Savo An QUESTION 22 A company is engaged in the packaging of a superior quality tea in jars of 250 g each. The company is of the view that as long as the jars contains 250 g of tea, the process is under control. Based on a sample of 100 jars, a 90% confidence interval for the average weight of tea contained in the jars is found to be (251 , 253). Can we conclude that the process is under control at 10% significance level? Do not reject Ho, the process is gone out of control. Reject Ho, the process is gone out of control. Reject Ho, the process is under control. Do not reject Ho, the process is under control. Click Save and Submit to save and submit. Click Save All Answers to save all answers. Save All Answer Save and SuQUESTION 23 Assume that the margin of error is 0.644 lb and the population standard deviation is known to be 1.5 1b. How many students must be randomly selected to estimate the mean weight of students in one age group using a 99% confidence level? QUESTION 24 A random sample of 55 light bulbs had a mean lifetime of 595 hours. A 90% confidence interval for the population mean was (590,600). Which one of the following statements is the correct interpretation of the results? Of all the bulbs 90% of the light bulbs in the sample had lifetimes between 590 hours and 600 hours None of these statements is true . With probability 90%, the confidence interval (590,600) contains the true mean lifetime We are 90% confident that the interval (590,600) contains the true mean lifetime QUESTION 25 The average monthly electricity consumption for a sample of 100 families is 1500 units. Assuming the standard deviation of electric consumption of all families is 160 units, find the lower limit of t he 90% confidence interval estimating the actual mean electric consumption. Round your answer to two decimal places. Click Save and Submit to save and submit. Click Save All Answers to save all answers. Save All AnsweTake Test: Homework 4 *Test Information Description . You are not allowed to use tables of distributions. If you answer a question using the z- table or t-table, your answer will be considered wrong. . You have to use the following online calculators: . http://davidmlane.com/hyperstat/z_table.html . http://www.statdistributions.com/t/ . http://www.statdistributions.comormal/
