Confidence Intervals Quiz

A sample of 30 women finds the mean height to be 62.3 in and the standard deviation to be 1.5 in. Find the margin of error of women's heights with a 95% CL.

• 1.699
• 0.56
• 0.537
• 19.325

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CCSS.HSS.IC.B.4

Which of the following does NOT have an affect on the width of a confidence interval?

• Sample mean
• t*
• Sample standard deviation
• Sample size

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

• increasing the confidence level, increasing the sample size
• decreasing the confidence level, decreasing the sample size
• increasing the confidence level, decreasing the sample size
• decreasing the confidence level, increasing the sample size.

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CCSS.HSS.IC.B.4

A 90% confidence interval for the mean speed driven by cars on East Main St. is given by (21, 45). What was the margin of error of this study?

• 12
• 24
• 33
• None of these.

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CCSS.HSS.IC.B.4

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

• We are 95% confident that the true mean calorie content can be found with a sample of 150 to 350 cupcakes.
• We are 95% confident that the true mean calorie content in cupcakes is between 150 and 350 calories.
• We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.
• None of these are correct.

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CCSS.HSS.IC.B.4

The 99% confidence interval for a proportion is (0.54, 0.72). What is p̂?

• 0.63

• 0.18

• 0.09

• 0.66

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CCSS.HSS.IC.B.4

If 1757 represents "yes" voters out of 2584, construct a 95% confidence interval for the "no" group.

• [.662,.698]

• [.298,.342]

• [.302,.338]

• [.288,.352]

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CCSS.HSS.IC.B.4

We have calculated a 95% confidence interval and would prefer for our next confidence interval to have a smaller margin of error without losing any confidence. In order to do this, we can....

• Change the t* value to a smaller number.

• Take a larger sample.

• Take a smaller sample.

• None of the Above

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CCSS.HSS.IC.B.4

As confidence level increases, margin of error...

• increases.

• decreases.

• stays the same.

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CCSS.HSS.IC.B.4

Choose the appropriate confidence interval for the situation:

After watching a horror film, 34 out of 50 people reported problems getting to sleep.

• z confidence interval for a mean

• t confidence interval for a mean

• z confidence interval for a proportion

• t confidence interval for a proportion