AP Statistics Confidence Intervals

Mark wants to know the percent of people in Phoenix that ride the bus. He goes to Target and asks the first 80 people that come into the store and finds that 20 of them rode the bus. Can he calculate a confidence interval?

• Yes, all conditions are met.

• No, the sample was not randomly collected

• No, the sample is not independent.

• No, the sampling distribution is not normal.

A nutritionist found that in a sample of 80 families, 22% said they are apples at least once a week. Construct the 90% CI for the population proportion.

• (0.144, 0.296)

• (0.190, 0.250)

• (0.704, 0.856)

• (0.129, 0.311)

Juan polls a random sample of 300 WHS students and finds that 30% like to read mystery novels. Can he calculate a confidence interval?

• Yes, all conditions are met.

• No, the sample was not randomly collected

• No, the sample is not independent.

• No, the sampling distribution is not normal.

A large sample has mean of 7.1 and Standard Error of 2.3.

Construct a 90% Confidence Interval for the population mean µ (to two decimal places).

• (3.32, 10.88)

• (3.8, 7.1)

• (3.3, 10.9)

• (3.3165, 10.8835)

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 value.

• 0.90

• 1.155

• 1.645

• ±1.645

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 Margin of Error to two decimal places.

• 1.90

• 1.89

• 1.899

• 1.99

A population has a standard deviation of σ = 17.3. How large of a sample must be drawn so that a 95% confidence interval for µ will have a Margin of Error equal to 1.4?

• 586.6

• 587

• 586

• 585

A person selects a random sample of 15 credit cards and determines the annual interest rate, in percent, of each one. The sample mean is 12.42 with a sample standard deviation of 1.3. It is desired to construct a 90% Confidence Interval.

Find the Standard Error to three decimal places.

• 0.336

• 0.33566

• 13.156

• 0.087

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

Find the Critical Value for an 86% Confidence Level.

• -1.48

• 1.48

• 1.282

• -1.47