1. A 99% confidence interval for population mean needs to be calculated with margin of error equal to 4.
If σ = 15, what sample size is needed in this study? A. 94
2. A continuous random variable may assume _____. A. all values in an interval or collection of intervals
3. A continuous random variable may assume _____. A. any value in an interval or collection of intervals
4. A population has a mean of 180 and a standard deviation of 24. A sample of 64 observations will be taken. The probability that the mean from that sample will be between 183 and 186 is _____. A. 0.1359
5. A population has a mean of 80 and a standard deviation of 7. A sample of 49 observations will be taken. The probability that the mean from that sample will be larger than 82 is _____. A. 0228
6. A population has a mean of 84 and a standard deviation of 12. A sample of 36 observations will be taken. The probability that the sample mean will be between 80.54 and 88.9 is _____. A. .9511
7. A population of size 1,000 has a proportion of .5. Therefore, the proportion and the standard deviation of the sample proportion for samples of size 100 are _____. A. .5 and .050
8. A probability distribution for all possible values of a sample statistic is known as a _____. A. sampling distribution
9. 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? A. If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure.
10. A random sample of 25 statistics examinations was selected. 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 _____. A. 69.29 to 82.71
11. A random variable that can assume only a finite number of values is referred to as a(n) _____. A. discrete random variable
12. A sample of 400 observations will be taken from an infinite population. The population proportion equals .8. The probability that the sample proportion will be greater than 0.83 is _____. A. .0668
13. A sample of 51 observations will be taken from an infinite population. The population proportion equals .85. The probability that the sample proportion will be between .9115 and .946 is _____. A. .0819
14. A sample of 66 observations will be taken from an infinite population. The population proportion equals .12. The probability that the sample proportion will be less than .1768 is _____. A. 9222
15. A subset of a population selected to represent the population is a _____. A. sample
16. A theorem that allows us to use the normal probability distribution to approximate the sampling distribution of sample means and sample proportions whenever the sample size is large is known as the _____. A. central limit theorem
17. All of the following are true about the standard error of the mean EXCEPT _____. A. it is larger than the standard deviation of the population
18. An apartment complex developer is considering building apartments in College Town, but first wants to do a market study. A sample was selected of monthly rent values for 70 studio apartments in College Town. The sample mean is $490.80. Based on past experience, the developer assumes a known value of Population Standard Deviation s = $55 for the population standard deviation. A. 117
19. An estimate of a population parameter that provides an interval believed to contain the value of the parameter is known as the _____. A. interval estimate
20. An interval estimate is used to estimate _____. A. a population parameter
21. As a general rule, the sampling distribution of the sample proportions can be approximated by a normal probability distribution whenever _____. A. np ≥ 5 and n(1 − p) ≥ 5
22. As the number of degrees of freedom for a t distribution increases, the difference between the t distribution and the standard normal distribution _____. A. becomes smaller
23.As the sample size increases, the _____. A. standard error of the mean decreases
24. As the sample size increases, the margin of error _____. A. decreases
25. Assume z is a standard normal random variable. Then P(1.20 ≤ z ≤ 1.85) equals _____. A. .0829
26. Assume z is a standard normal random variable. Then P(-1.20 ≤ z ≤ 1.50) equals _____. A. .8181
27. Assume z is a standard normal random variable. Then P(-1.96 ≤ z ≤ -1.4) equals _____. A. 0558
28. Assume z is a standard normal random variable. Then P(z ≥ 2.11) equals _____. A. .0174
29. For the interval estimation of μ when σ is assumed known, the proper distribution to use is the _____. A. standard normal distribution
30. If the margin of error in an interval estimate of μ is 4.6, the interval estimate equals _____. A. x +- 4.6
31. If the mean of a normal distribution is negative, _____. A. the median and mode must also be negative
32. If we consider the simple random sampling process as an experiment, the sample mean is _____. A. a random variable
33. In a standard normal distribution, the range of values of z is from _____. A. minus infinity to infinity
34. 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 _____. A. .133
35. 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 .95 probability, the margin of error is approximately _____. A. .26
36. 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 _____. A. 8.74 to 9.26 hours
37. It is known that the variance of a population equals 1,936. A random sample of 121 has been selected from the population. There is a .95 probability that the sample mean will provide a margin of error of _____. A. 7.84 or less
38. Larger values of the standard deviation result in a normal curve that is _____. A. wider and flatter
39. Probability Distribution
x
10
20
30
40
f(x)
.2
.3
.4
.1
Refer to Exhibit 5-6. The expected value of x equals _____. A. 24
40. Probability Distribution
x
10
20
30
40
f(x)
.2
.3
.4
.1
Refer to Exhibit 5-6. The variance of x equals _____. A. 84
41. Suppose x is a normally distributed random variable with a mean of 8 and a standard deviation of 4. The probability that x is between 1.48 and 15.56 is _____. A. .9190
42. Suppose x is a normally distributed random variable with a mean of 5 and a variance of 4. The probability that x is greater than 10.52 is _____. A. .0029
43. The ability of an interval estimate to contain the value of the population parameter is described by the _____. A. confidence level
44. The assembly time for a product is uniformly distributed between 6 and 10 minutes. The probability density function has what value in the interval between 6 and 10? A. .25
45. The assembly time for a product is uniformly distributed between 6 and 10 minutes. The probability of assembling the product in 7 minutes or more is _____. A. 75
46. The assembly time for a product is uniformly distributed between 6 and 10 minutes. The expected assembly time (in minutes) is _____. A. 8
47. The basis for using a normal probability distribution to approximate the sampling distribution of and is _____. A. the central limit theorem
48. The expected value of a random variable is the _____. A. measure of the central location of a random variable
49. The following data were collected from a simple random sample from an infinite population.
13 15 14 16 12
Refer to Exhibit 7-1. The point estimate of the population mean _____ A. is 14
50. The following data were collected from a simple random sample from an infinite population.
13 15 14 16 12
Refer to Exhibit 7-1. The mean of the population _____. A. could be any value
51. The general form of an interval estimate of a population mean or population proportion is the _____ plus or minus the _____. A. point estimate, margin of error
52. The highest point of a normal curve occurs at _____. A. the mean
53. The manager of a grocery store has selected 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 1 minute.
Refer to Exhibit 8-2. The standard error of the mean equals _____. A. .1
54. The manager of a grocery store has selected 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 1 minute.
Refer to Exhibit 8-2. With a .95 probability, the sample mean will provide a margin of error of _____. A. .196
55. The manager of a grocery store has selected 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 1 minute.
Refer to Exhibit 8-2. If the confidence coefficient is reduced to .80, the standard error of the mean _____. A. remains unchanged
56. The manager of a grocery store has selected 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 1 minute.
Refer to Exhibit 8-2. The 95% confidence interval for the average checkout time for all customers is _____. A. 2.804 to 3.196
57. The margin of error in an interval estimate of the population mean is a function of all of the following EXCEPT _____. A. sample mean
58. The number of electrical outages in a city varies from day to day. Assume that the number of electrical outages (x) in the city has the following probability distribution.
x
0
1
2
3
f(x)
0.80
0.15
0.04
0.01
The mean and the standard deviation for the number of electrical outages (respectively) are _____. A. 0.26 and .577
59. The population we want to make inferences about is the _____. A. target population
60. The probability distribution for the daily sales at Michael’s Co. is given below.
Daily Sales ($1000s)
Probability
40
.1
50
.4
60
.3
70
.2
Refer to Exhibit 5-2. The probability of having sales of at least $50,000 is _____. A. .90
61. The purpose of statistical inference is to provide information about the _____. A. population based upon information contained in the sample
62. The sampling distribution of the sample mean _____. A. is the probability distribution showing all possible values of the sample mean
63. The set of all elements of interest in a study is _____. A. a population
64. The standard deviation of is referred to as the _____. A. standard error of the mean
65. The t distribution should be used whenever _____. A. the sample standard deviation is used to estimate the population standard deviation
66. The t value with a 95% confidence and 24 degrees of freedom is _____. A. 2.064
67. The value of the _____ is used to estimate the value of the population parameter. A. sample statistic
68. The weight of an object, measured in grams, is an example of _____. A. a continuous random variable
69. The weight of items produced by a machine is normally distributed with a mean of 8 ounces and a standard deviation of 2 ounces.
Refer to Exhibit 6-5. What percentage of items will weigh between 6.4 and 8.9 ounces? A. .4617
70. The weight of items produced by a machine is normally distributed with a mean of 8 ounces and a standard deviation of 2 ounces.
Refer to Exhibit 6-5. What is the probability that a randomly selected item weighs exactly 8 ounces? A. 0
71. The z value for a 97.8% confidence interval estimation is _____. A. 2.29
72. When the level of confidence increases, the confidence interval _____. A. becomes wider
73. When the population has a normal distribution, the sampling distribution of is normally distributed _____. A. for any sample size
74. Whenever the probability is proportional to the length of the interval in which the random variable can assume a value, the random variable follows a(n) _____ distribution. A. uniform
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