Question 1

If university officials say that at least 70% of the voting student population supporting the fee increase,If the 95% confidence interval is [0.75,0.85],what conclusion can be drawn based on a 95% level of confidence?

Accepted Answer

A) 70% is not in the interval,need to take another sample 
B) 70% is not in the interval,so assume it will not be supported 
C) 70% is below the interval,so assume it will be supported 
D) Since this was not based on population,cannot make conclusion

Question 2

A random sample of 42 college graduates revealed that they worked an average of 5.5 years on the job before being promoted.The population standard deviation was 1.1 years.Using the 0.99 degree of confidence,what is the confidence interval for the population mean?

Accepted Answer

A) 5.04 and 5.96 
B) 5.06 and 5.94 
C) 2.67 and 8.33 
D) 4.40 and 6.60

Question 3

A 95% confidence interval infers that the population mean

Accepted Answer

A) is between 0 and 100% 
B) is within $\pm$1.96 standard deviations of the sample mean 
C) is within $\pm$1.96 standard errors of the sample mean 
D) is too large

Question 4

When deciding on the number of observations to include in a sample,what would favor larger sample sizes?

Accepted Answer

The answer of When deciding on the number of observations...

Question 5

A random sample of 20 items is selected from a population.To determine the appropriate critical t-value what number of degrees of freedom should be used?

Accepted Answer

A) 20 
B) 19 
C) 21 
D) 25

Question 6

The t distribution is more spread out and flatter at the center than the standard normal distribution.However,as the sample size increases,the t distribution curve approaches the standard normal distribution.

Accepted Answer

A) True 
 B)False

Question 7

The higher the degree of confidence,the larger the sample required to give a certain precision.

Accepted Answer

A) True 
 B)False

Question 8

Recently,a university surveyed recent graduates of the English Department for their starting salaries.Four hundred graduates returned the survey.The average salary was $25,000 with a standard deviation of $2,500.What is the best point estimate of the population mean?

Accepted Answer

A) $25,000 
B) $2,500 
C) 400 
D) $62.5

Question 9

If the size of a sample equals the size of the population,we would not expect any error in estimating the population parameter.

Accepted Answer

A) True 
 B)False

Question 10

A sample mean is the best point estimate of the

Accepted Answer

A) population standard deviation 
B) population median 
C) population mean 
D) the sample standard deviation

Question 11

The t distribution is a continuous distribution.

Accepted Answer

A) True 
 B)False

Question 12

A sample standard deviation is the best point estimate of the

Accepted Answer

A) population range 
B) population skewness 
C) population mode 
D) population standard deviation

Question 13

Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the Republican candidate for president.Using the 0.95 degree of confidence,what is the interval estimate for the population proportion (to the nearest tenth of a percent)?

Accepted Answer

A) 78.2% to 81.8% 
B) 69.2% to 86.4% 
C) 76.5% to 83.5% 
D) 77.7% to 82.3%

Question 14

Recently,a university surveyed recent graduates of the English Department for their starting salaries.Four hundred graduates returned the survey.The average salary was $25,000 with a standard deviation of $2,500.A 95% confidence interval is constructed.What does the confidence interval mean?

Accepted Answer

A) The population mean is in the interval 
B) The population mean is not in the interval 
C) The likelihood that any confidence interval based on a sample of 400 graduates will contain the population mean is 0.95 
D) There is a 5% chance that the computed interval does not contain the population mean

Question 15

A pharmaceutical company wanted to estimate the population mean of monthly sales for their 250 sales people.Forty sales people were randomly selected.Their mean monthly sales was $10,000 with a population standard deviation of $1000.Construct a 95% confidence interval for the population mean.

Accepted Answer

A) [9,690.1,10,309.9] 
B) [9,715.5,10,284.5] 
C) [8,040,11,960] 
D) [8,000,12,000]

Question 16

The distribution of Student's t is

Accepted Answer

A) symmetrical 
B) negatively skewed 
C) positively skewed 
D) a discrete probability distribution

Question 17

How is the t distribution similar to the standard z distribution?

Accepted Answer

A) Both are continuous distribution 
B) Both are bell-shaped 
C) Both are families of distributions 
D) A and B

Question 18

A random sample of 42 college graduates revealed that they worked an average of 5.5 years on the job before being promoted.The sample standard deviation was 1.1 years.Using the 0.99 degree of confidence,what is the confidence interval for the population mean?

Accepted Answer

A) 5.04 and 5.96 
B) 5.06 and 5.94 
C) 2.67 and 8.33 
D) 4.40 and 6.60

Question 19

Deciding on the number of observations to include in a sample is an important decision when planning a research study.What information is required to make this decision?

Accepted Answer

The answer of Deciding on the number of observations to...

Question 20

A student wanted to construct a 95% confidence interval for the average age of students in her statistics class.She randomly selected 9 students.Their average age was 19.1 years with a standard deviation of 1.5 years.What is the best point estimate for the population mean?

Accepted Answer

A) 2.1 years 
B) 1.5 years 
C) 19.1 years 
D) 9 years

Exam 9: Estimation and Confidence Intervals

If university officials say that at least 70% of the voting student population supporting the fee increase,If the 95% confidence interval is [0.75,0.85],what conclusion can be drawn based on a 95% level of confidence?

A random sample of 42 college graduates revealed that they worked an average of 5.5 years on the job before being promoted.The population standard deviation was 1.1 years.Using the 0.99 degree of confidence,what is the confidence interval for the population mean?

A 95% confidence interval infers that the population mean

When deciding on the number of observations to include in a sample,what would favor larger sample sizes?

A random sample of 20 items is selected from a population.To determine the appropriate critical t-value what number of degrees of freedom should be used?

The t distribution is more spread out and flatter at the center than the standard normal distribution.However,as the sample size increases,the t distribution curve approaches the standard normal distribution.

The higher the degree of confidence,the larger the sample required to give a certain precision.

Recently,a university surveyed recent graduates of the English Department for their starting salaries.Four hundred graduates returned the survey.The average salary was $25,000 with a standard deviation of $2,500.What is the best point estimate of the population mean?

If the size of a sample equals the size of the population,we would not expect any error in estimating the population parameter.

A sample mean is the best point estimate of the

The t distribution is a continuous distribution.

A sample standard deviation is the best point estimate of the

Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the Republican candidate for president.Using the 0.95 degree of confidence,what is the interval estimate for the population proportion (to the nearest tenth of a percent) ?

Recently,a university surveyed recent graduates of the English Department for their starting salaries.Four hundred graduates returned the survey.The average salary was $25,000 with a standard deviation of $2,500.A 95% confidence interval is constructed.What does the confidence interval mean?

A pharmaceutical company wanted to estimate the population mean of monthly sales for their 250 sales people.Forty sales people were randomly selected.Their mean monthly sales was $10,000 with a population standard deviation of $1000.Construct a 95% confidence interval for the population mean.

The distribution of Student's t is

How is the t distribution similar to the standard z distribution?

A random sample of 42 college graduates revealed that they worked an average of 5.5 years on the job before being promoted.The sample standard deviation was 1.1 years.Using the 0.99 degree of confidence,what is the confidence interval for the population mean?

Deciding on the number of observations to include in a sample is an important decision when planning a research study.What information is required to make this decision?

A student wanted to construct a 95% confidence interval for the average age of students in her statistics class.She randomly selected 9 students.Their average age was 19.1 years with a standard deviation of 1.5 years.What is the best point estimate for the population mean?