AP Stats 8.1-8.2 Confidence Intervals for Proportions

Which critical value corresponds to a 95% confidence level?

• 1.64

• 1.96

• 2.33

• 2.58

The standard error of the proportion is calculated as:

• 
• 
• 
• 

If the sample proportion is 0.4 and the sample size is 100, what is the standard error of the proportion?

• 0.049

• 0.069

• 0.059

• 0.039

For a 90% confidence level, the critical value is approximately:

• 1.28

• 1.64

• 1.96

• 2.33

What is the margin of error if the standard error of the proportion is 0.05 and the critical value for a 95% confidence level is 1.96?

• 0.098

• 0.1

• 0.09

• 0.2

How does increasing the sample size affect the margin of error, assuming the confidence level remains the same?

• Increases the margin of error

• Decreases the margin of error

• Does not affect the margin of error

• Initially decreases, then increases the margin of error

If the observed sample proportion is 0.55 and the margin of error is 0.05, what is the confidence interval?

• (0.50, 0.60)

• (0.45, 0.65)

• (0.55, 0.60)

• (0.50, 0.55)

If you want to decrease the width of the confidence interval without changing the sample size, what should you do?

• Increase the confidence level

• Decrease the confidence level

• Increase the z-score

• Decrease the z-score

What is the effect of increasing the confidence level on the margin of error, assuming the sample size remains constant?

• Increases the margin of error

• Decreases the margin of error

• Does not affect the margin of error

• Initially increases, then decreases the margin of error

Given a sample proportion of 0.3, a sample size of 150, and a 99% confidence level, what is the approximate margin of error?

• 0.13

• 0.08

• 0.12

• 0.09