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?