QBA Stone CHP 8 Questions with
Accurate Answers
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? correct answer
becomes narrower
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? correct answer 217
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? correct answer 9.8
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? correct answer 0.419 to 0.481
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? correct answer 19.200 to 20.800
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? correct
answer 83.00 to 85.00
, 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? correct answer 24.4 to
25.6
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?
correct answer The sample must have a normal distribution.
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?
correct answer normal distribution
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? correct
answer 170.2 to 189.8
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? correct answer 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? correct answer Increase the sample size.
An estimate of a population parameter that provides an interval of values
believed to contain the
value of the parameter is known as the? correct answer interval estimate
Accurate Answers
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? correct answer
becomes narrower
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? correct answer 217
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? correct answer 9.8
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? correct answer 0.419 to 0.481
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? correct answer 19.200 to 20.800
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? correct
answer 83.00 to 85.00
, 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? correct answer 24.4 to
25.6
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?
correct answer The sample must have a normal distribution.
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?
correct answer normal distribution
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? correct
answer 170.2 to 189.8
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? correct answer 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? correct answer Increase the sample size.
An estimate of a population parameter that provides an interval of values
believed to contain the
value of the parameter is known as the? correct answer interval estimate
