Confidence Intervals Mean Use Z or T?

A sample size of n = 64 is drawn from a population whose standard deviation is σ = 5.6.

Find the margin of error for a 99% confidence interval for µ.

• 1.799

• 1.798

• 1.803

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

What is the point estimate?

• 75

• 105.2

• 10

• 0.90

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

Find the Standard Error.

• 75

• 10

• 105.2

• 1.155

What is the t value associated with 90% confidence and a sample size of 15?

• 1.341

• 1.345

• 1.761

• 1.753

Why do we use a t-distribution instead of a z-distribution for means? 

• It reflects greater variability present in small samples.

• It allows us to decrease the margin of error without increasing our confidence level.

• It allows us to use the population standard deviation.

• None of these.

Which of the following does NOT have an affect on the width of a confidence interval?

• Sample mean

• t*

• Sample standard deviation

• Sample size

A survey was given to a random sample of 55 residents of a town of 30,000 people to determine whether they support a new plan to raise taxes in order to increase education spending. Of those surveyed, 8 respondents said they were in favor of the plan.

Should you use a one sample z interval or a one sample t interval for this problem?

• One Sample z Interval

• One Sample t Interval

A study of a large local high school tried to determine the mean amount of money that each student had saved. The study surveyed a random sample of 97 AP students in the high school and found a mean savings of 4100 dollars with a standard deviation of 500 dollars. Would you use a One Sample z Interval or a One Sample t Interval for this situation?

• One Sample z Interval

• One Sample t Interval

A study of a large local high school tried to determine the mean amount of money that each student had saved. The study surveyed a random sample of 97 AP students in the high school and found a mean savings of 4100 dollars with a standard deviation of 500 dollars. What would be the critical value for a 90% confidence interval in this situation?

A survey was given to a random sample of 1750 voters in the United States to ask about their preference for a presidential candidate. Of those surveyed, 595 respondents said that they preferred Candidate A.

Would you use a one sample z interval or a one sample t interval for this situation?

• One Sample z interval

• One Sample t Interval