Confidence Intervals Review

When interpreting the confidence interval, make sure that you are describing the 

• statistic
• parameter

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CCSS.HSS.IC.B.4

Which of the following is an example of an interval estimate?

• point estimate 
• critical value
• confidence interval
• statistic

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CCSS.HSS.IC.B.4

Complete the equation: 
point estimate +/- _____

• standard deviation
• margin of error
• critical value
• confidence level

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CCSS.HSS.IC.B.4

Increasing the sample size __________ the confidence interval. 

• increases
• decreases
• does not affect
• there is not enough evidence to determine the answer

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CCSS.HSS.IC.B.4

What can you do to reduce the margin of error? 

• increase the confidence level
• decrease the confidence level
• increase sample size
• decrease sample size

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CCSS.HSS.IC.B.4

The lifetime of a certain type of batter is known to be normally distributed with a standard deviation of 20 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. It is desired to construct a 99% confidence interval for the mean lifetime of this type of battery.

What is the Confidence Interval to one decimal place?

• (114.5, 125.6)

• (112.8, 127.4)

• (112.82, 127.38)

• (114.56, 125.64)

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CCSS.HSS.IC.B.4

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

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CCSS.HSS.IC.B.4

The variance of the t-distribution is 1

• True

• False

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CCSS.HSS.ID.A.4

A sample of 40 people owned an average of 1.35 apple products. It is known from a previous study that the population standard deviation of apple product ownership is 0.63 products. Construct a 95% confidence interval.

• (1.11, 1.58)
• (1.15, 1.55)
• (1.19, 1.51)
• (1.09, 1.61)

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CCSS.HSS.IC.B.4

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

• We are 95% confident that the true mean caloric content can be found with a sample of 150 to 350 cupcakes.

• We are 95% confident that the interval (150, 350) captures the true average caloric content.

• 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