QBA Stone CHP 8
In a sample of 400 voters, 360 indicated they favor the incumbent governor. The 95% confidence interval of voters not favoring the incumbent is?
0.071 to 0.129
In a random sample of 100 observations, = 0.2. The 95.44% confidence interval for P is?
0.120 to 0.280
A random sample of 1000 people was taken. Four hundred fifty of the people in the sample favored Candidate A. The 95% confidence interval for the true proportion of people who favors Candidate A is?
0.419 to 0.481
In a random sample of 144 observations, = 0.6. The 95% confidence interval for P is?
0.52 to 0.68
If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be?
0.9
If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be?
0.9
If we want to provide a 95% confidence interval for the mean of a population, the confidence coefficient is?
0.95
The following random sample from a population whose values were normally distributed was collected. 10 12 18 16 The 80% confidence interval for μ is?
11.009 to 16.991
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?
117
A sample of 225 elements from a population with a standard deviation of 75 is selected. The sample mean is 180. The 95% confidence interval for μ is?
170.2 to 189.8
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 is?
19.200 to 20.800
We are interested in conducting a study in order to determine what percentage of voters of a state would vote for the incumbent governor. What is the minimum size sample needed to estimate the population proportion with a margin of error of 0.05 or less at 95% confidence?
196
The t value for a 95% confidence interval estimation with 24 degrees of freedom is?
2.064
The z value for a 97.8% confidence interval estimation is?
2.29
A machine that produces a major part for an airplane engine is monitored closely. In the past, 10% of the parts produced would be defective. With a .95 probability, the sample size that needs to be taken if the desired margin of error is .04 or less is?
217
A random sample of 64 students at a university showed an average age of 25 years and a sample standard deviation of 2 years. The 98% confidence interval for the true average age of all students in the university is?
24.4 to 25.6
From a population with a variance of 900, a sample of 225 items is selected. At 95% confidence, the margin of error is?
3.92
In order to determine an interval for the mean of a population with unknown standard deviation a sample of 61 items is selected. The mean of the sample is determined to be 23. The number of degrees of freedom for reading the t value is?
60
The following random sample from a population whose values were normally distributed was collected. 10 8 11 11 The 95% confidence interval for μ is?
7.75 to 11.75
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?
7.84
It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken if the desired margin of error is 5 or less is?
75
A random sample of 49 statistics examinations was taken. The average score, in the sample, was 84 with a variance of 12.25. The 95% confidence interval for the average examination score of the population of the examinations is?
83.00 to 85.00
A population has a standard deviation of 50. A random sample of 100 items from this population is selected. The sample mean is determined to be 600. At 95% confidence, the margin of error is?
9.8
A sample of 20 items from a population with an unknown σ is selected in order to develop an interval estimate of μ. Which of the following is not necessary?
The sample must have a normal distribution.
From a population that is not normally distributed and whose standard deviation is not known, a sample of 6 items is selected to develop an interval estimate for the mean of the population (m)?
The sample size must be increased
From a population that is not normally distributed and whose standard deviation is not known, a sample of 6 items is selected to develop an interval estimate for the mean of the population (μ)?
The sample size must be increased.
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 μ?
becomes narrower
In interval estimation, as the sample size becomes larger, the interval estimate?
becomes narrower
As the number of degrees of freedom for a t distribution increases, the difference between the t distribution and the standard normal distribution?
becomes smaller
When the level of confidence decreases, the margin of error?
becomes smaller
Using an α = 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 wider
The ability of an interval estimate to contain the value of the population parameter is described by the?
confidence level
As the sample size increases, the margin of error?
decreases
An estimate of a population parameter that provides an interval of values believed to contain the value of the parameter is known as the?
interval estimate
An estimate of a population parameter that provides an interval of values believed to contain the value of the parameter is known as the?
interval estimate
The value added and subtracted from a point estimate in order to develop an interval estimate of the population parameter is known as the?
margin of error
In order to use the normal distribution for interval estimation of m when s is known and the sample is very small, the population?
must have a normal distribution
In order to use the normal distribution for interval estimation of μ when σ is known and the sample is very small, the population?
must have a normal distribution
When constructing a confidence interval for the population mean and the standard deviation of the sample is used, the degrees of freedom for the t distribution equals?
n-1
When constructing a confidence interval for the population mean and the standard deviation of the sample is used, the degrees of freedom for the t distribution equals?
n-1
When s is used to estimate σ, the margin of error is computed by using?
t distribution
Whenever the population standard deviation is unknown and the population has a normal or near-normal distribution, which distribution is used in developing an interval estimation?
t distribution
From a population that is normally distributed, a sample of 25 elements is selected and the standard deviation of the sample is computed. For the interval estimation of m, the proper distribution to use is the?
t distribution with 24 degrees of freedom
From a population that is normally distributed, a sample of 25 elements is selected and the standard deviation of the sample is computed. For the interval estimation of μ, the proper distribution to use is the?
t distribution with 24 degrees of freedom
When "s" is used to estimate "o~ (standard deviation)," the margin of error is computed by using?
t-distribution
When "s" is used to estimate "s," the margin of error is computed by using?
t-distribution
In determining the sample size necessary to estimate a population proportion, which of the following information is not needed?
the mean of the population
For the interval estimation of m when s is known and the sample is large, the proper distribution to use is?
the normal distribution
For the interval estimation of μ when σ is known and the sample is large, the proper distribution to use is?
the normal distribution
Whenever using the t distribution for interval estimation (when the sample size is very small), we must assume that?
the population is approximately normal
Whenever using the t distribution for interval estimation (when the sample size is very small), we must assume that?
the population is approximately normal
In order to use the normal distribution for interval estimation of m when s is known and the sample is very small?
the population must have a normal distribution
In developing an interval estimate, if the population standard deviation is unknown?
the sample standard deviation can be used
In interval estimation, the t distribution is applicable only when?
the sample standard deviation is used to estimate the population standard deviation
The absolute value of the difference between the point estimate and the population parameter it estimates is?
the sampling error
The absolute value of the difference between the point estimate and the population parameter it estimates is?
the sampling error
If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect?
the size of the confidence interval to increase
In general, higher confidence levels provide?
wider confidence intervals
After computing a confidence interval, the user believes the results are meaningless because the width of the interval is too large. Which one of the following is the best recommendation?
Increase the sample size
After computing a confidence interval, the user believes the results are meaningless because the width of the interval is too large. Which one of the following is the best recommendation?
Increase the sample size.
Which of the following best describes the form of the sampling distribution of the sample proportion?
It is approximately normal as long as np 5 and n(1-p) 5.
For which of the following values of P is the value of P(1 - P) maximized?
P = 0.50
For which of the following values of P is the value of P(1 - P) maximized?
P=0.50
An interval estimate is a range of values used to estimate?
a population parameter
A sample of 200 elements from a population with a known standard deviation is selected. For an interval estimation of μ, the proper distribution to use is the?
normal distribution
