Statistics
Question 1 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.A sample of 40 country CD recordings of Willie Nelson has been examined. The average playing time of these recordings is 51.3 minutes, and the standard deviation is s = 5.8 minutes.Using an appropriate t-multiplier, construct a 95% confidence interval for the mean playing time of all Willie Nelson recordings.Place your LOWER limit, in minutes, rounded to 2 decimal places, in the first blank. For example, 56.78 would be a legitimate entry. [removed] .Place your UPPER limit, in minutes, rounded to 2 decimal places, in the second blank. For example, 67.89 would be a legitimate entry. [removed]Question 2 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.A lawyer researched the average number of years served by 45 different justices on the Supreme Court. The average number of years served was 13.8 years with a standard deviation of 7.3 years. What is the 95% confidence interval estimate for the average number of years served by all Supreme Court justices? Place your limits, rounded to 1 decimal place, in the blanks. Place you lower limit in the first blank. [removed] Place your upper limit in the second blank. [removed] When entering your answer do not use any labels or symbols. Simply provide the numerical value. For example, 12.3 would be a legitimate entry.Question 3 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.The personnel department of a large corporation wants to estimate the family dental expenses of its employees to determine the feasibility of providing a dental insurance plan. A random sample of 12 employees reveals the following family dental expenses (in dollars): 115, 370, 250, 593, 540, 225, 177, 425, 318, 182, 275, and 228.Construct a 90% confidence interval estimate for the standard deviation of family dental expenses for all employees of this corporation.Place your LOWER limit, in dollars rounded to 1 decimal place, in the first blank. Do not use a dollar sign, a comma, or any other stray mark. For example, 123.4 would be a legitimate entry. [removed]Place your UPPER limit, in dollars rounded to 1 decimal place, in the second blank. Do not use a dollar sign, a comma, or any other stray mark. For example, 567.8 would be a legitimate entry. [removed]Question 4 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.The personnel department of a large corporation wants to estimate the family dental expenses of its employees to determine the feasibility of providing a dental insurance plan. A random sample of 12 employees reveals the following family dental expenses (in dollars): 115, 370, 250, 593, 540, 225, 177, 425, 318, 182, 275, and 228.Construct a 95% confidence interval estimate for the standard deviation of family dental expenses for all employees of this corporation.Place your LOWER limit, in dollars rounded to 1 decimal place, in the first blank. Do not use a dollar sign, a comma, or any other stray mark. For example, 123.4 would be a legitimate entry. [removed]Place your UPPER limit, in dollars rounded to 1 decimal place, in the second blank. Do not use a dollar sign, a comma, or any other stray mark. For example, 567.8 would be a legitimate entry. [removed]Question 5 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.Senior management of a consulting services firm is concerned about a growing decline in the firms weekly number of billable hours. The firm expects each professional employee to spend at least 40 hours per week on work. In an effort to understand this problem better, management would like to estimate the standard deviation of the number of hours their employees spend on work-related activities in a typical week. Rather than reviewing the records of all the firms full-time employees, the management randomly selected a sample of size 51 from the available frame. The sample mean and sample standard deviations were 48.5 and 7.5 hours, respectively.Construct a 99% confidence interval for the standard deviation of the number of hours this firms employees spend on work-related activities in a typical week.Place your LOWER limit, in hours, rounded to 1 decimal place, in the first blank. For example, 6.7 would be a legitimate entry. [removed]Place your UPPER limit, in hours, rounded to 1 decimal place, in the second blank. For example, 12.3 would be a legitimate entry. [removed]Question 6 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.The percent defective for parts produced by a manufacturing process is targeted at 4%. The process is monitored daily by taking samples of sizes n = 160 units. Suppose that todays sample contains 14 defectives.How many units would have to be sampled to be 95% confident that you can estimate the fraction of defective parts within 2% (using the information from todays sample–that is using the result that ^p = 0.0875)?Place your answer, as a whole number, in the blank. For example 567 would be a legitimate entry. [removed]Question 7 of 201.0 PointsAccepted characters: numbers, decimal point markers (period or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000), “E” or “e” (used in scientific notation). NOTE: For scientific notation, a period MUST be used as the decimal point marker.Complex numbers should be in the form (a + bi) where “a” and “b” need to have explicitly stated values.For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is valid whereas {9i} is not.The manufacturer of a new compact car claims the miles per gallon (mpg) for the gasoline consumption is mound-shaped and symmetric with a mean of 24.6 mpg and a standard deviation of 11.2 mpg. If 30 such cars are tested, what is the probability the average mpg achieved by these 30 cars will be greater than 27?Answer: [removed] Round your answer to 4 decimal places as necessary. For example, 0.1357 would be a legitimate entry.Part 2 of 3 -Question 8 of 201.0 PointsA food snack manufacturer samples 15 bags of pretzels off the assembly line and weighed their contents. If the sample mean is 10.0 and the sample standard deviation is 0.15, find the 95% confidence interval estimate for the true mean.[removed] A.(9.96, 10.04)[removed] B.(9.68, 10.32)[removed] C.(9.97, 10.80)[removed] D.(9.92, 10.08)Question 9 of 201.0 PointsThe t- distribution for developing a confidence interval for a mean has _____ degrees of freedom.[removed] A.n – 1[removed] B.n – 2[removed] C.n[removed] D.n + 1Question 10 of 201.0 PointsWhich of the following will make a confidence interval narrower and more precise?[removed] A.Smaller sample size and lower confidence level[removed] B.Larger sample size and higher confidence level[removed] C.Smaller sample size and higher confidence level[removed] D.Larger sample size and lower confidence levelQuestion 11 of 201.0 PointsA researcher wishes to know, with 98% confidence, the percentage of women who wear shoes that are too small for their feet. A previous study conducted by the Academy of Orthopedic Surgeons found that 80% of women wear shoes that are too small for their feet. If the researcher wants her estimate to be within 3% of the true proportion, how large a sample is necessary?[removed] A.966[removed] B.683[removed] C.183[removed] D.484Question 12 of 201.0 PointsA recent study of 750 Internet users in Europe found that 35% of Internet users were women. What is the 95% confidence interval estimate for the true proportion of women in Europe who use the Internet?[removed] A.0.321 < p < 0.379[removed] B.0.316 < p < 0.384[removed] C.0.309 < p < 0.391[removed] D.0.305 < p < 0.395Question 13 of 201.0 PointsAt a large department store, the average number of years of employment for a cashier is 5.7 with a standard deviation of 1.8 years. If the number of years of employment at this department store is normally distributed, what is the probability that a cashier selected at random has worked at the store for over 10 years?[removed] A.0.4916[removed] B.0.9916[removed] C.0.0084[removed] D.0.0054Question 14 of 201.0 PointsA previous study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams. How many nickels does a coin counter manufacturer need to weigh so that she can be 98% confident that her sample mean is within 25 milligrams of the true average weight of a nickel?[removed] A.36[removed] B.196[removed] C.239[removed] D.139Question 15 of 201.0 PointsIf you increase the confidence level, the confidence interval ____________.[removed] A.decreases[removed] B.may increase or decrease, depending on the sample data[removed] C.increases[removed] D.stays the sameQuestion 16 of 201.0 PointsCompute P( t20 _< - 0.95) where t20 has a t-distribution with 20 degrees of freedom.[removed] A.0.5334[removed] B.0.1767[removed] C.0.8233[removed] D.0.6466Question 17 of 201.0 PointsIn a study of elephants a researcher wishes to determine the average weight of a certain subspecies of elephants. From previous studies, the standard deviation of the weights of elephants in this subspecies is known to be 1500 pounds. How many elephants does the researcher need to weigh so that he can be 80% confident that the average weight of elephants in his sample is within 350 pounds of the true average weight for this subspecies?[removed] A.166[removed] B.31[removed] C.50[removed] D.39Question 18 of 201.0 PointsIn order to be accepted into a top university, applicants must score within the top 5% on the SAT exam. Given that SAT test scores are normally distributed with a mean of 1000 and a standard deviation of 200, what is the lowest possible score a student needs to qualify for acceptance into the university?[removed] A.1330[removed] B.1400[removed] C.1250[removed] D.1100Part 3 of 3 -Question 19 of 201.0 PointsA 90% confidence interval estimate for a population mean is determined to be 72.8 to 79.6. If the confidence level is reduced to 80%, the confidence interval becomes narrower.[removed] True[removed] FalseQuestion 20 of 201.0 PointsIn general, increasing the confidence level will narrow the confidence interval, and decreasing the confidence level widens the interval.[removed] True[removed] FalseNumber 6 and 16 I could not properly inset the symbol. Contact me if a confusion occur.
