7-4 Quiz: Confidence Intervals for Means

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

The 90% interval for a statistics test was given by 72 +- 7. What is the lower bound for the interval?

• 7
• 72
• 65
• 79

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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

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CCSS.HSS.IC.B.4

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 sample mean of this study?

• 12
• 24
• 33
• None of these.

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CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

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.

Tags

CCSS.HSS.IC.B.4

Why do we use a t-distribution instead of a z-distribution for means? 

• It reflects greater variability present in small samples.
• It allows us to decrease the margin of error without increasing our confidence level.
• It allows us to use the population standard deviation.
• 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

CCSS.HSS.IC.A.1

In a crash test of 15 troopers, collision repair costs are found to have a distribution that is approximately normal, with a mean of $1800 and a standard deviation of $950. Construct a 99% confidence interval for the repair cost. 

• (1070, 2530)
• (1273, 2326)
• (1799, 1801)
• None of these.

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CCSS.HSS.IC.B.4

Find the t* value for a 99% confidence interval with a sample of 23 people.

• 1.714
• 1.711
• 2.064
• None of these.