Intro to Confidence Intervals

What is the standard deviation of the distribution?

• 1010
• 20
• 60
• √20

You sample 16 students in your school, and they average 13 hours of TV a week. Assume the standard deviation is 3. Find a 99% Confidence Interval.

Which of the following is incorrect?

• μ = 13

• σ = 3

• Z = 1.645

• n = 16

True or False:

The larger your confidence interval is, the more sure (higher confidence level) you can be.

• True

• False

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 critical (z) value.

• 0.90

• 1.155

• 1.645

• ±1.645

Which one is the correct setup for this scenario?

300 hundred eggs were randomly chosen from a fish.

The mean weight was 0.978 g with a standard deviation of

0.042. Find the 95% confidence interval for the mean weight of the salmon eggs.

300 hundred eggs were randomly chosen from a fish.

The mean weight was 0.978 g with a standard deviation of

0.042. Find the 95% confidence interval for the mean weight of the salmon eggs.

• (0.973, 0.983)

• (1.936, 1.984)

• (0.971, 0.988)

A sample of 20 cupcakes found the interval for average calories to be (150, 350). Which is the correct interpretation of the 95% confidence interval?

• We are 95% confident that the true mean caloric content can be found with a sample of 150 to 350 cupcakes.

• We are 95% confident that the interval (150, 350) captures the true average caloric content.

• We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.

• None of these are correct.