Confidence Intervals for Means Practice 10th - 12th Grade Quiz

Confidence Intervals for Means Practice

Assessment

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Mike Parker

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Mathematics

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10th - 12th Grade

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Hard

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16 questions

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Multiple Choice

2 mins

1 pt

A random 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.

Based on the sample, we are 95% confident that true average caloric content is in the interval 150 to 350 calories

We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.

None of these are correct.

Multiple Choice

2 mins

1 pt

A quality control specialist at a glass factory must estimate the mean clarity rating for a new batch of glass using a sample of 18 glass sheets from the batch. Past investigations show that clarity ratings are normally distributed. The specialist decides to use a t-distribution rather than a z-distribution because ...

The t distribution is more accurate than a z distribution.

Clarity ratings for the entire bacth are normally distributed.

The t-distribution will create a narrower interval than z.

The standard deviation for the population is unknown.

Multiple Choice

5 mins

1 pt

Thirty randomly selected students took the calculus final. If the sample mean was 92 and the standard deviation was 9.4, construct a 99 percent confidence interval for the mean score of all students from which the sample was gathered.

89.08 < μ < 94.92

87.27 < μ < 96.73

87.29 < μ < 96.71

87.77 < μ < 96.23

Multiple Choice

2 mins

1 pt

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.

Multiple Choice

5 mins

1 pt

The lifetime of a certain type of battery 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)