Other Confidence Intervals

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

Given the Critical Value of Z = 2.11, find the Confidence Level.

• 96.52%

• 0.9652

• .9826

• 98.26%

A random sample of 50 12th-grade students was asked how long it took to get to school. The sample mean was 16.2 minutes, and the sample standard deviation was 12.3 minutes. Find a 95% confidence interval for the population mean time it takes 12th-grade students to get to school. (Give your answer in the form " (#,#) " with no spaces, and with answers rounded to the nearest tenth.)

A random sample of 50 12th-grade students was asked how long it took to get to school. The sample mean was 16.2 minutes, and the sample standard deviation was 12.3 minutes. Find a 90% confidence interval for the population mean time it takes 12th-grade students to get to school. (Give your answer in the form " (#,#) " with no spaces, and with answers rounded to the nearest tenth.)

A random sample of 25 baseball players from the 2017 Major League Baseball season was taken and the sample data was used to construct two confidence intervals for the population mean. One interval was (22.0, 42.8) The other interval was (19.9, 44.0). How would a 99% confidence interval compare to the intervals given above?

• The 99% confidence interval would be wider than both the 90% and 95% confidence intervals.

• The 99% confidence interval's width would fall between the 90% and 95% confidence intervals' widths.

• The 99% confidence interval would be more narrow than both the 90% and the 95% confidence intervals.

The weights of four randomly and independently selected bags of tomatoes labeled 5 pounds were found to be 5.1, 5.0, 5.3, and 5.1 pounds. Assume Normality. Find a 95% confidence interval for the mean weight of all bags of tomatoes based on this sample. (Give your answer in the form " (#,#) " with no spaces, and with answers rounded to the nearest tenth.)

I randomly select 25 students’ Math SAT scores and find the mean to be 600. I know the standard deviation of the population is 50. Find a 95% Confidence Interval.

Identify the Variables

• 25

• Z

• 50

• σ

• 600

• μ

• 1.96

• n

9 out of 25 students bring their lunch to school. Construct a 90% Confidence Interval for the proportion of students who bring their lunch to school.

What is the value of p?

• p = 9

• p = .36

• p = 2.78

• p = .64

A 95% confidence interval for the mean reading achievement score for a population of third-grade students is (44.2, 54.2). Suppose you compute a 99% confidence interval using the same information. Which of the following statements is correct?

• The intervals have the same width.

• The 99% interval is shorter.

• The 99% interval is longer.

• The answer can’t be determined from the information given.

• None of the mentioned options