CHAPTER EIGHT INTERVAL estimate MULTIPLE selection QUESTIONS In the adhering to multiple an option questions, circle the exactly answer. 1. As soon as s is offered to estimate (, the margin the error is computed by utilizing a. Normal circulation b. T distribution c. The average of the sample d. The median of the population Answer: b 2. As the variety of degrees of flexibility for a t circulation increases, the difference between the t distribution and the traditional normal circulation a. Becomes bigger b. Becomes smaller c. Stays the same d. No one of these alternatives is correct.

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Answer: b 3. Because that the interval estimation of (when (is known and the sample is large, the suitable distribution to usage is a. The normal circulation b. The t distribution with n degrees of flexibility c. The t distribution with n + 1 degrees of freedom d. The t circulation with n + 2 levels of liberty Answer: a 4. An estimate of a population parameter that offers an expression of values believed to contain the value of the parameter is recognized as the a. Confidence level b. Interval estimate c. Parameter worth d. Populace estimate Answer: b 5.

The value included and subtracted from a suggest estimate in stimulate to build an interval estimate of the populace parameter is recognized as the a. Trust level b. Margin the error c. Parameter estimate d. Interval estimate Answer: b 6. If one interval calculation is said to be created at the 90% trust level, the confidence coefficient would certainly be a. 0. 1 b. 0. 95 c. 0. 9 d. 0. 05 Answer: c 7. Anytime the population standard deviation is unknown and also the population has a regular or near-normal distribution, which circulation is provided in occurring an term estimation? a. Standard circulation b. Circulation c. Alpha circulation d. T circulation Answer: d 8. In term estimation, the t distribution is applicable only once a. The population has a typical of less than 30 b. The sample standard deviation is provided to calculation the population standard deviation c. The variance that the populace is well-known d. The traditional deviation that the population is recognized Answer: b 9. In arising an term estimate, if the population standard deviation is unknown a. It is difficult to construct an interval calculation b. The standard deviation is came down on using the variety c. The sample traditional deviation have the right to be used d. T is assumed the the population standard deviation is 1 Answer: c 10. In order to use the normal distribution for interval estimate of (when (is known and also the sample is really small, the population a. Should be very large b. Must have actually a normal circulation c. Have the right to have any kind of distribution d. Must have actually a median of at least 1 Answer: b 11. Indigenous a population that is not typically distributed and whose typical deviation is not known, a sample that 6 items is selected to build an interval estimate for the mean of the populace ((). A. The normal circulation can be used. B. The t distribution with 5 levels of flexibility must it is in used.. The t distribution with 6 levels of freedom must it is in used. D. The sample size have to be increased. Answer: d 12. A sample that 200 elements from a populace is selected, and the typical deviation that the sample is computed. Because that an interval estimate of (, the ideal distribution to use is the a. Normal distribution b. T circulation with 200 levels of freedom c. T circulation with 201 degrees of liberty d. T distribution with 202 levels of liberty Answer: a 13. Native a population that is normally distributed, a sample the 25 facets is selected and the standard deviation that the sample is computed.

For the interval estimate of (, the proper distribution to usage is the a. Normal distribution b. T circulation with 25 levels of flexibility c. T distribution with 26 levels of flexibility d. T distribution with 24 degrees of liberty Answer: d 14. The z value for a 97. 8% confidence interval estimation is a. 2. 02 b. 1. 96 c. 2. 00 d. 2. 29 Answer: d 15. The t value with a 95% confidence and also 24 levels of liberty is a. 1. 711 b. 2. 064 c. 2. 492 d. 2. 069 Answer: b 16. Together the sample dimension increases, the margin that error a. Rises b. Reduce c. Continues to be the exact same d. Boosts or decreases depending upon the dimension of the mean

Answer: b 17. Because that which of the complying with values of ns is the value of P(1 – P) maximized? a. Ns = 0. 99 b. P = 0. 90 c. Ns = 0. 01 d. P = 0. 50 Answer: d 18. A 95% trust interval for a populace mean is identified to be 100 come 120. If the confidence coefficient is diminished to 0. 90, the interval because that (a. Becomes narrow b. Becomes more comprehensive c. Go not readjust d. I do not care 0. 1 Answer: a 19. Making use of an (= 0. 04 a confidence interval for a population proportion is figured out to it is in 0. 65 come 0. 75. If the level of significance is decreased, the interval for the population proportion a. I do not care narrower. Becomes wider c. Does not readjust d. Stays the exact same Answer: b 20. The capacity of one interval estimate to contain the worth of the population parameter is defined by the a. Confidence level b. Levels of liberty c. An accurate value of the population mean (d. Degrees of freedom minus 1 Answer: a 21. After computer a to trust interval, the user to trust the results are meaningless because the width of the expression is also large. Which among the complying with is the finest recommendation? a. Boost the level the confidence because that the interval. B. Decrease the sample size. C. Rise the sample size.. Alleviate the population variance. Answer: c 22. If we adjust a 95% confidence interval calculation to a 99% confidence interval estimate, we deserve to expect a. The size of the trust interval to increase b. The dimension of the confidence interval to decrease c. The size of the trust interval to remain the exact same d. The sample dimension to boost Answer: a 23. In general, greater confidence levels administer a. Broader confidence intervals b. Narrower confidence intervals c. A smaller standard error d. Unbiased estimates Answer: a 24. An interval estimate is a variety of values used to calculation a. He form of the population’s distribution b. The sampling circulation c. A sample statistic d. A populace parameter Answer: d 25. In identify the sample size vital to estimate a populace proportion, i beg your pardon of the complying with information is not needed? a. The best margin that error that have the right to be tolerated b. The trust level compelled c. A preliminary calculation of the true populace proportion ns d. The typical of the population Answer: d 26. Whenever using the t distribution for interval estimation (when the sample size is really small), we have to assume the a. The sample has a mean of at least 30. The sampling distribution is not regular c. The population is about normal d. The finite population correction factor is vital Answer: c 27. A sample that 20 items from a population with an unknown (is selected in bespeak to develop an interval calculation of (. I beg your pardon of the adhering to is not necessary? a. We should assume the population has a normal distribution. B. We should use a t distribution. C. Sample standard deviation must be used to calculation (. D. The sample must have a normal distribution. Answer: d 28. A random sample the 144 observations has a typical of 20, a median of 21, and a setting of 22.

The population standard deviation is well-known to same 4. 8. The 95. 44% trust interval because that the population mean is a. 15. 2 to 24. 8 b. 19. 200 come 20. 800 c. 19. 216 come 20. 784 d. 21. 2 to 22. 8 Answer: b 29. The sample size required to administer a margin the error that 2 or much less with a. 95 probability when the population standard deviation equals 11 is a. 10 b. 11 c. 116 d. 117 Answer: d 30. It is known that the population variance equates to 484. V a 0. 95 probability, the sample dimension that requirements to be taken if the preferred margin the error is 5 or less is a. 25 b. 74 c. 189 d. 75 Answer: d 31.

When creating a confidence interval because that the population mean and the traditional deviation of the sample is used, the levels of freedom for the t circulation equals a. N-1 b. N c. 29 d. 30 Answer: a 32. Which of the following ideal describes the type of the sampling circulation of the sample proportion? a. When standardized, the is precisely the typical normal distribution. B. Once standardized, it is the t distribution. C. It is about normal as lengthy as n (30. D. That is about normal as lengthy as np (5 and n(1-p) (5. Answer: d 33. In a arbitrarily sample the 144 observations, = 0. 6. The 95% confidence interval for p is. 0. 52 come 0. 68 b. 0. 144 come 0. 200 c. 0. 60 come 0. 70 d. 0. 50 come 0. 70 Answer: a 34. A maker that produce a major part for an plane engine is monitored closely. In the past, 10% that the parts developed would it is in defective. V a .95 probability, the sample size that requirements to be taken if the wanted margin of error is. 04 or less is a. 110 b. 111 c. 216 d. 217 Answer: d 35. We space interested in conducting a examine in order to identify what percent of voter of a state would vote for the incumbent governor. What is the minimum dimension sample required to calculation the population proportion v a margin the error that 0. 5 or much less at 95% confidence? a. 200 b. 100 c. 58 d. 196 Answer: d 36. In a sample of 400 voters, 360 suggested they favor the incumbent governor. The 95% trust interval the voters not favoring the incumbent is a. 0. 871 come 0. 929 b. 0. 120 to 0. 280 c. 0. 765 to 0. 835 d. 0. 071 to 0. 129 Answer: d exhibition 8-1 In bespeak to calculation the median time spent on the computer system terminals per college student at a neighborhood university, data were collected for a sample that 81 service students end a one week period. I think the populace standard deviation is 1. 8 hours. 37. Refer to Exhibit 8-1. The conventional error the the typical is. 7. 50 b. 0. 39 c. 2. 00 d. 0. 20 Answer: d 38. Refer to Exhibit 8-1. Through a 0. 95 probability, the margin the error is roughly a. 0. 39 b. 1. 96 c. 0. 20 d. 1. 64 Answer: a 39. Describe Exhibit 8-1. If the sample typical is 9 hours, climate the 95% to trust interval is a. 7. 04 come 110. 96 hours b. 7. 36 come 10. 64 hours c. 7. 80 come 10. 20 hrs d. 8. 61 come 9. 39 hrs Answer: d exhibition 8-2 A random sample that 121 automobiles travel on an interstate verified an average speed that 65 mph. From previous information, it is known that the traditional deviation that the population is 22 mph. 40. Refer to Exhibit 8-2.

If we room interested in determining an interval estimate for (at 96. 6% confidence, the Z worth to use is a. 1. 96 b. 0. 483 c. 2. 12 d. 1. 645 Answer: c 41. Refer to Exhibit 8-2. The traditional error of the average is a. 22. 00 b. 96. 60 c. 4. 24 d. 2. 00 Answer: d 42. Describe Exhibit 8-2. If the trust coefficient is diminished to 0. 9, the traditional error of the median a. Will increase b. Will decrease c. Stays unchanged d. Becomes negative Answer: c 43. Describe Exhibit 8-2. The 96. 6% to trust interval because that (is a. 63. 00 come 67. 00 b. 60. 76 come 69. 24 c. 61. 08 to 68. 92 d. 60. 00 to 80. 00 Answer: b 44.

Refer to exhibit 8-2. If the sample size was 100 (other determinants remain unchanged), the interval because that (would a. Not change b. Become narrower c. Become wider d. Become zero Answer: c troubles 1. Girlfriend are given the complying with information derived from a sample that 5 monitorings taken indigenous a populace that has actually a common distribution. 9472935477 develop a 98% confidence interval estimate for the median of the population. Answer: 50. 29 come 105. 71 2. Many civilization who purchase X-Game gaming systems over the holidays have complained the the equipment they purchased to be defective. In a sample that 1200 devices sold, 18 devices were defective.. Recognize a 95% trust interval for the percentage of defective systems. B. If 1. 5 million X-Games were sold over the holidays, recognize an interval because that the number of defectives in sales. Answers: a. 0. 00812 to 0. 02188 (rounded) b. 12,184 come 32,816 3. The average monthly electric bill that a random sample that 256 inhabitants of a city is $90 through a traditional deviation that $24. A. Construct a 90% confidence interval because that the mean monthly electrical bills of all residents. B. Construct a 95% to trust interval for the average monthly electric bills of every residents. Answers: a. 87. 5325 to 92. 4675 b. 87. 6 come 92. 94 4. Two hundred students are enrolled in an economics class. ~ the very first examination, a random sample the 6 files was selected. The qualities were 65, 75, 89, 71, 70 and 80. A. Identify the traditional error that the mean. B. What assumption must it is in made before we have the right to determine an interval because that the median grade of every the college student in the class? describe why. C. Assume the assumption of part b is met. Administer a 95% trust interval because that the typical grade of all the students in the class. Answers: a. 3. 474 b. Since (is approximated from s, we have to assume the distribution of all the grades is normal. C. 6. 07 come 83. 93 5. A statistician selected a sample that 16 account receivable and also determined the median of the sample to be $5,000 through a traditional deviation of $400. That reported that the sample information indicated the mean of the populace ranges native $4,739. 80 come $5,260. 20. The neglected come report what to trust coefficient he had used. Based on the over information, identify the confidence coefficient that was used. Assume the population has a common distribution. Answer: 0. 98 6. A researcher is interested in determining the average number of years employee of a agency stay through the company.

If past details shows a traditional deviation the 7 months, what dimension sample should be bring away so the at 95% to trust the margin of error will be 2 months or less? Answer: 48 7. A sample the 144 can be ~ of coffee showed an average weight of 16 ounces with a standard deviation of 1. 2 ounces. A. Construct a 68. 36% confidence interval for the mean of the population. B. Build a 97% trust interval for the typical of the population. C. Talk about why the answer in parts a and also b room different. Answers: a. 31. 88 to 32. 12 b. 31. 75 to 32. 25 c. Together the level of confidence increases, the confidence interval becomes wider. 8.

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A random sample that 121 checking accounts in ~ a bank showed one average everyday balance of $280. The standard deviation that the populace is known to be $66. A. Is it necessary to know anything around the form of the circulation of the account balances in stimulate to do an interval calculation of the average of every the account balances? Explain. B. Uncover the traditional error that the mean. C. Provide a point estimate of the populace mean. D. Construct a 80% confidence interval approximates for the mean. E. Build a 95% trust interval because that the mean. Answers: a. No, the sample is large and the conventional deviation that the population is known.. 6 c. 280 d. 272. 31 to 287. 69 e. 268. 24 to 291. 76 9. A arbitrarily sample that 53 monitorings was taken. The mean in the sample to be 90 v a variance of 400. A. Construct a 98% confidence interval because that (. B. Construct a 99% to trust interval because that (. C. Comment on why the 98% and also 99% to trust intervals are different. D. What would certainly you intend to take place to the confidence interval in component a if the sample size was increased? Be sure to define your answer. Answers: a. 83. 41 to 96. 59 b. 82. 65 to 97. 34 c. Together the level of trust increases, the confidence interval gets wider. D. Decrease due to the fact that the sampling error decreased. 0. A brand-new brand of coco bar is being market tested. Four hundred that the new chocolate bars were offered to consumers to try. The consumer were asked even if it is they liked or disliked the chocolate bar. You are provided their responses below. ResponseFrequency Liked300 Disliked100 400 a. What is the suggest estimate for the relationship of civilization who liked the chocolate bar? b. Build a 95% trust interval for the true ratio of civilization who chosen the cacao bar. C. V a. 95 probability, how huge of a sample demands to it is in taken to carry out a margin of error the 3% or less? Answers: a. 0. 75 b. 0. 71 come 0. 79 c. 801 1. If the typical deviation that the life time of washing makers is approximated to it is in 900 hours, how large a sample have to be bring away in bespeak to it is in 97% confident the the margin of error will certainly not exceed 100 hours? Answer: 382 12. The manager the a department keep wants to identify what relationship of people who go into the keep use the store’s credit cards for their purchases. What size sample need to he take it so the at 95% confidence the error will certainly not be an ext than 6%? Answer: 267 13. An Excel printout the the descriptive procedures of day-to-day checking account balances (in dollars) of customers of an initial Daisy financial institution is displayed below.

Develop a 95% to trust interval estimate for the median of the population of the checking balances. |Account Balance details | |Mean |4828. 29 | |Median |5115. 25 | |Mode |4976. 50 | |Standard Deviation |1143. 57 | |Sample Variance |1307763. 49 | |Kurtosis |8. 63 | |Skewness |-3. 06 | |Range |4968. 50 | |Minimum |600. 00 | |Maximum |5568. 50 | amount |173818. 50 | |Count |36. 00 | Answer: 4441. 382 come 5215. 198 14. Information regarding the price that a role of camera film (35 mm, 24 exposure) because that a sample the 12 cities an international is displayed below. Recognize a 95% confidence interval for the populace mean. |Price of Film information | | |Mean |5. 3667 | |Standard Error |0. 7409 | |Median |4. 8700 | |Standard Deviation |2. 666 | |Sample Variance |6. 5873 | |Kurtosis |4. 0201 | |Skewness |1. 8041 | |Range |9. 4100 | |Minimum |2. 7300 | |Maximum |12. 1400 | |Sum |64. 4000 | |Count |12. 0000 | Answer: 3. 736 to 6. 997