Confidence Interval Review

What is confidence interval?

• A period of time in mathematics.

• An interval that always has 95% accuracy.

• A range of values we are confident that a value lies between

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What does the displayed image show?

• The average rate of change.

• A normal distribution.

• A cubic function.

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Which z-value is used for a 95% confidence interval?

• 2.58

• 2.33

• 1.96

• 1.28

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When do we use t-distribution?

• When we don't have the standard deviation of the population.

• When the sample size is 10% of the population size.

• When the standard deviation of the population is 95% or higher.

• When the population size is greater than the sample size.

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How does t-distribution compare to a Normal curve?

• closer together

• more spread

• they are equal distributed

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What is the degrees of freedom equal to?

• n

• n + 1

• 1 - n

• n - 1

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.

• (1.15, 1.55)

• (1.04, 1.64)

• (1.23, 1.56)

• (1.12, 1.63)

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We measure the height of 40 randomly selected women, in which the mean height is 175cm. We also know the standard deviation is 20cm. Which of the following represents a 95% Confidence Interval?

• 135cm ± 20cm

• 175cm ± 6.2cm

• 155cm ± 6.2cm

• 175cm ± 35cm

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What is the t value associated with 90% confidence and a sample size of 15?

• 1.683

• 1.234

• 1.437

• 1.761

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 a sample of 20 cupcakes will find 250 calories per cupcake.

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

• None of the above.

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