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Q:
In determining the sample size necessary to estimate a population proportion, which of the following information is notneeded?
a. the maximum margin of error that can be tolerated
b. the confidence level required
c. a preliminary estimate of the true population proportion p
d. the mean of the population
Q:
Using an = 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 proportiona. becomes narrowerb. becomes widerc. does not changed. Not enough information is provided to answer this question.
Q:
We can use the normal distribution to make confidence interval estimates for the population proportion, p, when
Q:
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
a. 25
b. 74
c. 189
d. 75
Q:
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
a. 10
b. 11
c. 116
d. 117
Q:
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. 95% of the sample of employees has a systolic blood pressure between 123 and 139.
b. If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure.
c. 95% of the population of employees has a systolic blood pressure between 123 and 139.
d. If the sampling procedure were repeated many times, 95% of the sample means would be between 123 and 139.
Q:
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
a. 70.02 to 81.98
b. 69.82 to 82.18
c. 70.06 to 81.94
d. 69.48 to 82.52
Q:
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
a. 24.301 to 25.699
b. 24.385 to 25.615
c. 23.200 to 26.800
d. 23.236 to 26.764
Q:
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 isa. 6.000 to 14.000b. 9.846 to 10.154c. 8.384 to 11.616d. 8.462 to 11.538
Q:
The tvalue with a 95% confidence and 24 degrees of freedom is
a. 1.711
b. 2.064
c. 2.492
d. 2.069
Q:
As the number of degrees of freedom for a tdistribution increases, the difference between the tdistribution and the standard normal distribution
a. becomes larger
b. becomes smaller
c. stays the same
d. None of the other answers are correct.
Q:
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 . Which of the following statements is true?a. The standard normal distribution can be used.b. The t distribution with 50 degrees of freedom must be used.c. The t distribution with 49 degrees of freedom must be used.d. The sample size must be increased in order to develop an interval estimate.
Q:
From a population that is normally distributed with an unknown standard deviation, a sample of 25 elements is selected. For the interval estimation of , the proper distribution to use is thea. standard normal distributionb. z distributionc. t distribution with 26 degrees of freedomd. t distribution with 24 degrees of freedom
Q:
Whenever using the tdistribution in interval estimation, we must assume that thea. sample size is less than 30b. degrees of freedom equals n-1c. population is approximately normald. finite population correction factor is necessary
Q:
The tdistribution should be used whenever
a. the sample size is less than 30
b. the sample standard deviation is used to estimate the population standard deviation
c. the population is not normally distributed
d. None of the other answers are correct.
Q:
Whenever the population standard deviation is unknown, which distribution is used in developing an interval estimate for a population mean?
a. standard distribution
b. zdistribution
c. binomial distribution
d. tdistribution
Q:
An auto manufacturer wants to estimate the annual income of owners of a particular model of automobile. A random sample of 200 current owners is taken. The population standard deviation is known. Which Excel function would notbe appropriate to use to construct a confidence interval estimate?
a. NORMSINV
b. COUNTIF
c. AVERAGE
d. STDEV
Q:
A bank manager wishes to estimate the average waiting time for customers in line for tellers. A random sample of 50 times is measured and the average waiting time is 5.7 minutes. The population standard deviation of waiting time is 2 minutes. Which Excel function would be used to construct a confidence interval estimate?
a. CONFIDENCE
b. NORMINV
c. TINV
d. INT
Q:
In developing an interval estimate of the population mean, if the population standard deviation is unknown
a. it is impossible to develop an interval estimate
b. a sample proportion can be used
c. the sample standard deviation and tdistribution can be used
d. None of the other answers are correct.
Q:
If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect the
a. width of the confidence interval to increase
b. width of the confidence interval to decrease
c. width of the confidence interval to remain the same
d. sample size to increase
Q:
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 ï
a. becomes narrower
b. becomes wider
c. does not change
d. becomes 0.1
Q:
When the level of confidence increases, the confidence interval
a. stays the same
b. becomes wider
c. becomes narrower
d. cannot tell from the information given
Q:
In general, higher confidence levels provide
a. wider confidence intervals
b. narrower confidence intervals
c. a smaller standard error
d. unbiased estimates
Q:
Refer to Exhibit 8-3. If the sample size was 25 (other factors remain unchanged), the interval for ïwould
a. not change
b. become narrower
c. become wider
d. become zero
Q:
Refer to Exhibit 8-3. The 86.9% confidence interval for ïis
a. 46.500 to 73.500
b. 57.735 to 62.265
c. 59.131 to 60.869
d. 50 to 70
Q:
Refer to Exhibit 8-3. The value to use for the standard error of the mean is
a. 13.5
b. 9
c. 2.26
d. 1.5
Q:
Exhibit 8-3A 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 ïat 86.9% confidence, the zvalue to use isa. 1.96b. 1.31c. 1.51d. 2.00
Q:
Refer to Exhibit 8-2. The 95% confidence interval for the average checkout time of all customers isa. 3 to 5b. 1.36 to 4.64c. 2.804 to 3.196d. 1.04 to 4.96
Q:
Refer to Exhibit 8-2. If the confidence coefficient is reduced to 0.80, the standard error of the mean
a. will increase
b. will decrease
c. remains unchanged
d. becomes negative
Q:
Refer to Exhibit 8-2. With a .95 probability, the sample mean will provide a margin of error of
a. 0.95
b. 0.10
c. .196
d. 1.96
Q:
Exhibit 8-2The 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 equalsa. 0.001b. 0.010c. 0.100d. 1.000
Q:
Refer to Exhibit 8-1. If the sample mean is 9 hours, then the 95% confidence interval is approximatelya. 7.04 to 110.96 hoursb. 7.36 to 10.64 hoursc. 7.80 to 10.20 hoursd. 8.74 to 9.26 hours
Q:
Refer to Exhibit 8-1. With a 0.95 probability, the margin of error is approximately
a. 0.26
b. 1.96
c. 0.21
d. 1.64
Q:
Exhibit 8-1In 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 isa. 7.5b. 0.014c. 0.160d. 0.133
Q:
A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean isa. 15.2 to 24.8b. 19.2 to 20.8c. 19.216 to 20.784d. 21.2 to 22.8
Q:
It is known that the variance of a population equals 1,936. A random sample of 121 has been taken from the population. There is a .95 probability that the sample mean will provide a margin of error of
a. 7.84 or less
b. 31.36 or less
c. 344.96 or less
d. 1,936 or less
Q:
The zvalue for a 97.8% confidence interval estimation is
a. 2.02
b. 1.96
c. 2.00
d. 2.29
Q:
For the interval estimation of when is assumed known, the proper distribution to use is thea. standard normal distributionb. tdistribution with ndegrees of freedomc. tdistribution with n- 1 degrees of freedomd. tdistribution with n- 2 degrees of freedom
Q:
If we want to provide a 95% confidence interval for the mean of a population, the confidence coefficient isa. 0.485b. 1.96c. 0.95d. 1.645
Q:
If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be
a. 0.1
b. 0.95
c. 0.9
d. 0.05
Q:
The ability of an interval estimate to contain the value of the population parameter is described by thea. confidence levelb. degrees of freedomc. precise value of the population mean d. None of the other answers are correct.
Q:
The confidence associated with an interval estimate is called the
a. level of significance
b. degree of association
c. confidence level
d. precision
Q:
As the sample size increases, the margin of error
a. increases
b. decreases
c. stays the same
d. None of the other answers are correct.
Q:
An estimate of a population parameter that provides an interval believed to contain the value of the parameter is known as the
a. confidence level
b. interval estimate
c. parameter value
d. population estimate
Q:
An interval estimate is used to estimate
a. the shape of the population's distribution
b. the sampling distribution
c. a sample statistic
d. a population parameter
Q:
The mean of the t distribution isa. 0b. .5c. 1d. problem specific
Q:
The expression used to compute an interval estimate of may depend on any of the following factors excepta. the sample sizeb. whether the population standard deviation is knownc. whether the population has an approximately normal distributiond. whether there is sampling error
Q:
In determining an interval estimate of a population mean when t is unknown, we use a tdistribution witha. degrees of freedomb. degrees of freedoc. n-1 degrees of freedomd. ndegrees of freedom
Q:
We can reduce the margin of error in an interval estimate of pby doing any of the following except
a. increasing the sample size
b. increasing the planning value p* to .5
c. increasing the level of significance
d. reducing the confidence coefficient
Q:
The sample size that guarantees all estimates of proportions will meet the margin of error requirements is computed using a planning value of pequal to
a. .01
b. .50
c. .51
d. .99
Q:
The use of the normal probability distribution as an approximation of the sampling distribution of is based on the condition that both npand n(1 " p) equal or exceed
a. .05
b. 5
c. 10
d. 30
Q:
To compute the minimum sample size for an interval estimate of , we must first determine all of the following excepta. desired margin of errorb. confidence levelc. population standard deviationd. degrees of freedom
Q:
The probability that the interval estimation procedure will generate an interval that does not contain the actual value of the population parameter being estimated is the
a. level of significance
b. confidence level
c. confidence coefficient
d. error factor
Q:
The tdistribution is a family of similar probability distributions, with each individual distribution depending on a parameter known as the
a. finite correction factor
b. sample size
c. degrees of freedom
d. standard deviation
Q:
If the margin of error in an interval estimate of is 4.6, the interval estimate equalsa. b. c. d.
Q:
As the degrees of freedom increase, the tdistribution approaches the
a. uniform distribution
b. normal distribution
c. exponential distribution
d. pdistribution
Q:
A population of size 1,000 has a proportion of 0.5. Therefore, the proportion and the standard deviation of the sample proportion for samples of size 100 are
a. 500 and 0.047
b. 500 and 0.050
c. 0.5 and 0.047
d. 0.5 and 0.050
Q:
A random sample of 150 people was taken from a very large population. Ninety of the people in the sample were females. The standard error of the proportion of females is
a. 0.0016
b. 0.2400
c. 0.1600
d. 0.0400
Q:
Random samples of size 525 are taken from a process (an infinite population) whose population proportion is 0.3. The standard deviation of the sample proportions (i.e., the standard error of the proportion) is
a. 0.0004
b. 0.2100
c. 0.3000
d. 0.0200
Q:
The probability distribution of all possible values of the sample proportion is the
a. probability density function of b. sampling distribution of c. same as , since it considers all possible values of the sample proportion
d. sampling distribution of
Q:
Refer to Exhibit 7-5. Which of the following best describes the form of the sampling distribution of the sample mean for this situation?
a. Approximately normal because the sample size is small relative to the population size.
b. Approximately normal because of the central limit theorem.
c. exactly normal
d. None of the alternative answers is correct.
Q:
Refer to Exhibit 7-5. The mean and the standard deviation of the sampling distribution of the sample means are
a. 8.7 and 1.94
b. 36 and 1.94
c. 36 and 1.86
d. 36 and 8
Q:
Refer to Exhibit 7-4. In this problem the 0.22 isa. a parameterb. a statisticc. the standard error of the meand. the average content of colognes in the long run
Q:
Refer to Exhibit 7-4. The point estimate of the mean content of all bottles is
a. 0.22
b. 4
c. 121
d. 0.02
Q:
Exhibit 7-4A random sample of 121 bottles of cologne showed an average content of 4 ounces. It is known that the standard deviation of the contents (i.e., of the population) is 0.22 ounces.Refer to Exhibit 7-4. The standard error of the mean equalsa. 0.3636b. 0.0331c. 0.0200d. 4.000
Q:
A population has a mean of 53 and a standard deviation of 21. A sample of 49 observations will be taken. The probability that the sample mean will be greater than 57.95 isa. 0b. .0495c. .4505d. None of the alternative answers is correct.
Q:
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 isa. 0.0347b. 0.7200c. 0.9511d. None of the alternative answers is correct.
Q:
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
b. 0.8185
c. 0.3413
d. 0.4772
Q:
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. 0.5228
b. 0.9772
c. 0.4772
d. 0.0228
Q:
A sample of 92 observations is taken from a process (an infinite population). The sampling distribution of is approximately normal because
a. is always approximately normally distributed
b. the sample size is small in comparison to the population size
c. of the central limit theorem
d. None of the alternative answers is correct.
Q:
A sample of 24 observations is taken from a population that has 150 elements. The sampling distribution of is
a. approximately normal because is always approximately normally distributed
b. approximately normal because the sample size is large in comparison to the population size
c. approximately normal because of the central limit theorem
d. normal if the population is normally distributed
Q:
For a population with an unknown distribution, the form of the sampling distribution of the sample mean is
a. approximately normal for all sample sizes
b. exactly normal for large sample sizes
c. exactly normal for all sample sizes
d. approximately normal for large sample sizes
Q:
Whenever the population has a normal probability distribution, the sampling distribution of is a normal probability distribution for
a. only large sample sizes
b. only small sample sizes
c. any sample size
d. only samples of size thirty or greater
Q:
As the sample size becomes larger, the sampling distribution of the sample mean approaches a
a. binomial distribution
b. Poisson distribution
c. hypergeometric distribution
d. None of the alternative answers is correct.
Q:
The fact that the sampling distribution of the sample mean can be approximated by a normal probability distribution whenever the sample size is large is based on the
a. central limit theorem
b. fact that there are tables of areas for the normal distribution
c. assumption that the population has a normal distribution
d. All of these answers are correct.
Q:
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. approximation theorem
b. normal probability theorem
c. central limit theorem
d. central normality theorem
Q:
Random samples of size 36 are taken from a process (an infinite population) whose mean and standard deviation are 20 and 15, respectively. The distribution of the population is unknown. The mean and the standard error of the distribution of sample mean are
a. 36 and 15
b. 20 and 15
c. 20 and 0.417
d. 20 and 2.5
Q:
Random samples of size 81 are taken from a process (an infinite population) whose mean and standard deviation are 200 and 18, respectively. The distribution of the population is unknown. The mean and the standard error of the distribution of sample means are
a. 200 and 18
b. 81 and 18
c. 9 and 2
d. 200 and 2
Q:
Random samples of size 49 are taken from a population that has 200 elements, a mean of 180, and a variance of 196. The distribution of the population is unknown. The mean and the standard error of the distribution of sample means are
a. 180 and 24.39
b. 180 and 28
c. 180 and 1.74
d. 180 and 2
Q:
Doubling the size of the sample will
a. reduce the standard error of the mean to one-half its current value
b. reduce the standard error of the mean to approximately 70% of its current value
c. have no effect on the standard error of the mean
d. double the standard error of the mean