STAT 121 Exam 2025 Questions Verified Answers
An administrator in a very large company wants to estimate the mean level of nitrogen
oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars.
Historically, nitrogen oxide levels have been known to be Normally distributed with a
standard deviation of 0.15 g/ml. What is the parameter of interest that the administrator
wants to estimate?
The mean level of nitrogen oxide of all cars of a particular model in the very large fleet.
An administrator in a very large company wants to estimate the mean level of nitrogen
oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars.
Historically, nitrogen oxide levels have been known to be Normally distributed with a
standard deviation of 0.15 g/ml. What is the parameter of interest that the administrator
wants to estimate? What statistic is used to estimate the parameter of interest?
The mean level of nitrogen oxide of a sample of cars of a particular model in the very large
fleet.
True or False: Statistical inference can be defined as making generalizations about the
population based on sample data.
True
A study of child preferences for milk chocolate was performed. Based on sample results,
researchers were 95% confident that the proportion of children that liked milk chocolate was
between 0.75 and 0.93. What type of inference is being used?
Interval estimation
Based on sample results, researchers estimate that μμ, the mean height of all female
students in a university, is 64 inches. What type of inference is being used?
Point Estimation
, True or False: Point estimation is a form of statistical inference in which, based on the sample
data, we estimate the unknown parameter of interest using a range of plausible values.
False
A recent study claimed that half of all college students "drink to get drunk" at least once in a
while. Believing that the true proportion is much lower, the College Alcohol Study interviews
an SRS of 14,941 college students about their drinking habits and finds that 7,352 of them
occasionally "drink to get drunk". What type of statistical inference is this? Point Estimation,
Interval Estimation or Hypothesis Testing?
Hypothesis Testing
What is the z* associated with 98% confidence?
2.326
In confidence interval estimation, we use a confidence interval to estimate......?
The value of a population parameter
An administrator in a very large company wants to estimate the mean level of nitrogen
oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars.
Historically, nitrogen oxide levels have been known to be Normally distributed with a
standard deviation of 0.15 g/ml. A 98% confidence interval estimate for the mean nitrogen
oxide level was computed. What do we hope to find in this confidence interval?
The value of μ, the mean level of nitrogen oxides emitted by all cars of a particular model in
their fleet.
Suppose the correct computation of the 98% confidence interval estimate is (0.87 g/ml, 0.97
g/ml). Which of the following is a correct interpretation of this 98% confidence interval?
We are 98% confident that the value of the mean nitrogen oxide level, μμ, for all cars of a
particular model is between 0.87 g/ml and 0.97 g/ml.
An administrator in a very large company wants to estimate the mean level of nitrogen
oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars.
Historically, nitrogen oxide levels have been known to be Normally distributed with a
standard deviation of 0.15 g/ml. What is the parameter of interest that the administrator
wants to estimate?
The mean level of nitrogen oxide of all cars of a particular model in the very large fleet.
An administrator in a very large company wants to estimate the mean level of nitrogen
oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars.
Historically, nitrogen oxide levels have been known to be Normally distributed with a
standard deviation of 0.15 g/ml. What is the parameter of interest that the administrator
wants to estimate? What statistic is used to estimate the parameter of interest?
The mean level of nitrogen oxide of a sample of cars of a particular model in the very large
fleet.
True or False: Statistical inference can be defined as making generalizations about the
population based on sample data.
True
A study of child preferences for milk chocolate was performed. Based on sample results,
researchers were 95% confident that the proportion of children that liked milk chocolate was
between 0.75 and 0.93. What type of inference is being used?
Interval estimation
Based on sample results, researchers estimate that μμ, the mean height of all female
students in a university, is 64 inches. What type of inference is being used?
Point Estimation
, True or False: Point estimation is a form of statistical inference in which, based on the sample
data, we estimate the unknown parameter of interest using a range of plausible values.
False
A recent study claimed that half of all college students "drink to get drunk" at least once in a
while. Believing that the true proportion is much lower, the College Alcohol Study interviews
an SRS of 14,941 college students about their drinking habits and finds that 7,352 of them
occasionally "drink to get drunk". What type of statistical inference is this? Point Estimation,
Interval Estimation or Hypothesis Testing?
Hypothesis Testing
What is the z* associated with 98% confidence?
2.326
In confidence interval estimation, we use a confidence interval to estimate......?
The value of a population parameter
An administrator in a very large company wants to estimate the mean level of nitrogen
oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars.
Historically, nitrogen oxide levels have been known to be Normally distributed with a
standard deviation of 0.15 g/ml. A 98% confidence interval estimate for the mean nitrogen
oxide level was computed. What do we hope to find in this confidence interval?
The value of μ, the mean level of nitrogen oxides emitted by all cars of a particular model in
their fleet.
Suppose the correct computation of the 98% confidence interval estimate is (0.87 g/ml, 0.97
g/ml). Which of the following is a correct interpretation of this 98% confidence interval?
We are 98% confident that the value of the mean nitrogen oxide level, μμ, for all cars of a
particular model is between 0.87 g/ml and 0.97 g/ml.
