Proportion Confidence Intervals

A preliminary study suggests that 87% of people agree on an issue. How large must your sample size be so you could be within ± 3% of p calculate at 90% confidence?

• 7

• 466

• 5

• 338

Which confidence would result in a wider interval (assuming nothing else changed), 91% or 97%?

• 97%, z* is larger for higher confidence intervals

• 97%, the standard error is larger for higher confidence intervals

• 91%, z* is larger for lower confidence intervals

• 91%, the standard error is smaller for lower confidence intervals

What is the margin of error of this sample?

• 0.28

• 0.14

• 0.342

• 0.684

In a survey of 104 students, it was found that 79 went to the homecoming game this year.

Calculate a 99% confidence interval for p.

• (.59, .79)

• (.62, .85)

• (.60, .90)

• (.65, .87)

What is the point estimate, p̂, of this sample?

• .322

• .342

• .465

• .511

Find the Critical Value for an 86% Confidence Level for a proportion.

• 1.48

• -1.48

• 1.96

• -1.96

What is the margin of error of this sample?

• .21

• .344

• .14

• .342

Which of the following changes to a study would result in a narrower confidence interval?

• decreasing the confidence level, increasing the sample size

• increasing the confidence level, decreasing the sample size

• increasing the confidence level, increasing the sample size

• decreasing the confidence level, decreasing the sample size

Which is the correct program to use on the TI-84 calculator in order to calculate confidence intervals for population proportion?

• STAT->

  TESTS->

  7: ZInterval

• STAT->

  TESTS->

  1-PropZint

• STAT->

  TESTS->

  3: 2-SampZTest

• 
  STAT->

  TESTS->

  2:T-Test

It was found that in a sample of 90 teenage boys, 70% of them have received speeding tickets. What is the 95% confidence interval of the true proportion of teenage boys who have received speeding tickets?

• (0.61, 0.80)

• (0.591, 0.812)

• (0.584, 0.830)

• (0.65, 0.85)