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Confidence Intervals and Sample Size

Authored by Barbara White

Mathematics

11th - 12th Grade

Confidence Intervals and Sample Size
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25 questions

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1.

MULTIPLE CHOICE QUESTION

2 mins • 1 pt

What is the margin of error for the interval (6.8, 12.9)?

9.85

3.05

3.50

6.8

2.

MULTIPLE CHOICE QUESTION

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.

3.

MULTIPLE CHOICE QUESTION

2 mins • 1 pt

A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of 45 CEOs. The interval was ($139,048, $154,144). Give a practical interpretation of the interval.

90% of the sampled CEOs have salaries that fell in the interval $139,048 to $154,144
We are 90% confident that the mean salary of all CEOs in the electronics industry falls in the interval $139,048 to $154,144. 
90% of all CEOs in the electronics industry have salaries that fall between $139,048 to $154,144
We are 90% confident that the mean salary of the sampled CEOs falls in the interval $139,048 to $154,144.

4.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

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

0.63

0.18

0.09

0.66

5.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

A 90% confidence interval for a population mean is determined to be 800 to 900. If the confidence is increased to 95% confidence while the sample statistics and sample size remain the same, the confidence interval

becomes wider

becomes narrower

does not change

6.

MULTIPLE CHOICE QUESTION

3 mins • 1 pt

A random sample of 85 sixth-graders in a large city take a course designed to improve scores on a reading comprehension test. Based on this sample, a 90% confidence interval for the mean improvement in test scores for all sixth-graders in the city taking this course is found to be (12.6, 14.8). Which of the following are the sample mean and margin of error on which this interval is based?

Sample Mean = 13.7; Margin of Error = 1.1
Sample mean = 13.7; Margin of Error = 2.2
Sample mean is unknown; Margin of Error = 2.2

7.

MULTIPLE CHOICE QUESTION

2 mins • 1 pt

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

Sample mean
Confidence Level
Sample standard deviation
Sample size

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