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A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is 15.2 to 24.8 19.2 to 20.8 19.216 to 20.784 21.2 to 22.8 Question 6 10 points Save Exhibit 8-1 In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one-week period. Assume the population standard deviation is 1.2 hours. Refer to Exhibit 8-1. The standard error of the mean is 7.5 0.014 0.160 0.133 Question 7 10 points Save Exhibit 8-1 In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one-week period. Assume the population standard deviation is 1.2 hours. Refer to Exhibit 8-1. With a 0.95 probability, the margin of error is approximately 0.26 1.96 0.21 1.64 Question 8 10 points Save Exhibit 8-1 In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one-week period. Assume the population standard deviation is 1.2 hours. Refer to Exhibit 8-1. If the sample mean is 9 hours, then the 95% confidence interval is approximately 7.04 to 110.96 hours 7.36 to 10.64 hours 7.80 to 10.20 hours 8.74 to 9.26 hours Question 9 10 points Save Exhibit 8-2 The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the checkout time is one minute. Refer to Exhibit 8-2. The standard error of the mean equals 0.001 0.010 0.100 1.000 Question 10 10 points Save Exhibit 8-2 The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the checkout time is one minute. Refer to Exhibit 8-2. With a .95 probability, the sample mean will provide a margin of error of 0.95 0.10 .196 1.96 Question 11 10 points Save Exhibit 8-2 The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the checkout time is one minute. Refer to Exhibit 8-2. If the confidence coefficient is reduced to 0.80, the standard error of the mean will increase will decrease remains unchanged becomes negative Question 12 10 points Save Exhibit 8-2 The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the checkout time is one minute. Refer to Exhibit 8-2. The 95% confidence interval for the average checkout time of all customers is 3 to 5 1.36 to 4.64 2.804 to 3.196 1.04 to 4.96 Question 13 10 points Save Exhibit 8-3 A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph. Refer to Exhibit 8-3. If we are interested in determining an interval estimate for m at 86.9% confidence, the z value to use is 1.96 1.31 1.51 2.00 Question 14 10 points Save Exhibit 8-3 A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph. Refer to Exhibit 8-3. The value to use for the standard error of the mean is 13.5 9 2.26 1.5 Question 15 10 points Save Exhibit 8-3 A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph. Refer to Exhibit 8-3. The 86.9% confidence interval for m is 46.500 to 73.500 57.735 to 62.265 59.131 to 60.869 50 to 70 Question 16 10 points Save Exhibit 8-3 A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph. Refer to Exhibit 8-3. If the sample size was 25 (other factors remain unchanged), the interval for m would not change become narrower become wider become zero Question 17 10 points Save A 95% confidence interval for a population mean is determined to be 100 to 120. If the confidence coefficient is reduced to 0.90, the interval for m becomes narrower becomes wider does not change becomes 0.1 Question 18 10 points Save If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect the width of the confidence interval to increase width of the confidence interval to decrease width of the confidence interval to remain the same sample size to increase Question 19 10 points Save From a population that is normally distributed with an unknown standard deviation, a sample of 25 elements is selected. For the interval estimation of m, the proper distribution to use is the standard normal distribution z distribution t distribution with 26 degrees of freedom t distribution with 24 degrees of freedom Question 20 10 points Save From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for m. Which of the following statements is true? The standard normal distribution can be used. The t distribution with 50 degrees of freedom must be used. The t distribution with 49 degrees of freedom must be used. The sample size must be increased in order to develop an interval estimate. Question 21 10 points Save As the number of degrees of freedom for a t distribution increases, the difference between the t distribution and the standard normal distribution becomes larger becomes smaller stays the same None of the other answers are correct. Question 22 10 points Save The t value with a 95% confidence and 24 degrees of freedom is 1.711 2.064 2.492 2.069 Question 23 10 points Save A sample of 26 elements from a normally distributed population is selected. The sample mean is 10 with a standard deviation of 4. The 95% confidence interval for m is 6.000 to 14.000 9.846 to 10.154 8.384 to 11.616 8.462 to 11.538 Question 24 10 points Save A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is 24.301 to 25.699 24.385 to 25.615 23.200 to 26.800 23.236 to 26.764 Question 25 10 points Save A random sample of 25 statistics examinations was taken. The average score in the sample was 76 with a variance of 144. Assuming the scores are normally distributed, the 99% confidence interval for the population average examination score is 70.02 to 81.98 69.82 to 82.18 70.06 to 81.94 69.48 to 82.52 Question 26 10 points Save A random sample of 25 employees of a local company has been measured. A 95% confidence interval estimate for the mean systolic blood pressure for all company employees is 123 to 139. Which of the following statements is valid? 95% of the sample of employees has a systolic blood pressure between 123 and 139. If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure. 95% of the population of employees has a systolic blood pressure between 123 and 139. If the sampling procedure were repeated many times, 95% of the sample means would be between 123 and 139. Question 27 10 points Save To estimate a population mean, the sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is 10 11 116 117 Question 28 10 points Save It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less is 25 74 189 75 Question 29 10 points Save Using an a = 0.04, a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion becomes narrower becomes wider does not change Not enough information is provided to answer this question. Question 30 10 points Save For which of the following values of p is the value of p(1 - p) maximized? p = 0.99 p = 0.90 p = 1.0 p = 0.50 Question 31 10 points Save A random sample of 25 observations was taken from a normally distributed population. The average in the sample was 84.6 with a variance of 400. Construct a 90% confidence interval for m. 77.756 to 91.444 73.412 to 95.788 78.021 to 91.179 79.474 to 89.726 Question 32 10 points Save You are given the following information obtained from a random sample of 4 observations taken from a large, normally distributed population. 25 47 32 56 Construct a 95% confidence interval for the mean of the population. 26.210 to 53.790 28.427 to 51.573 28.058 to 51.942 17.613 to 62.387 Question 33 10 points Save If the standard deviation of the lifetimes of vacuum cleaners is estimated to be 300 hours, how large of a sample must be taken in order to be 97% confident that the margin of error will not exceed 40 hours? 300 264 265 299 Question 34 10 points Save A researcher is interested in determining the average number of years employees of a company stay with the company. If past information shows a standard deviation of 7 months, what size sample should be taken so that at 95% confidence the margin of error will be 2 months or less? 50 48 47 30 Question 35 10 points Save In a random sample of 500 college students, 23% say that they read or watch the news every day. Develop a 90% confidence interval for the population proportion. 0.199 to 0.261 0.184 to 0.276 0.189 to 0.271 0.225 to 0.235 Question 36 10 points Save Six hundred consumers were asked whether they would like to purchase a domestic or a foreign automobile. Their responses are given below. Preference Frequency Domestic 240 Foreign 360 Develop a 95% confidence interval for the proportion of all consumers who prefer to purchase domestic automobiles. 0.6180 to 0.7154 0.3671 to 0.4329 0.3608 to 0.4392 0.3750 to 0.4250 Question 37 10 points Save A university planner wants to determine the proportion of spring semester students who will attend summer school. She surveys 32 current students discovering that 12 will return for summer school. With a 0.95 probability, how large of a sample would have to be taken to provide a margin of error of 3% or less? 1001 1000 32 50 Question 38 10 points Save A health club annually surveys its members. Last year, 33% of the members said they use the treadmill at least 4 times a week. How large of sample should be taken this year to estimate the percentage of members who use the treadmill at least 4 times a week? The estimate is desired to have a margin of error of 5% with a 95% level of confidence. 340 50 30 15

 

Paper#9808 | Written in 18-Jul-2015

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