Practice Margin of Error in Statistics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The maximum expected difference between a sample statistic and the population parameter, typically expressed as \pm a value.

When a poll says '52% \pm 3%,' that 3% is the margin of error. It means the true value is probably within 3 percentage points of 52%, so between 49% and 55%.

Example 1

hard
A poll of 400 voters found 55% support a policy. Calculate the margin of error for a 95% confidence interval.

Example 2

hard
How does quadrupling the sample size affect the margin of error?

Example 3

hard
A 95% CI for a mean is 50 \pm 3. What is the margin of error, and what would it be if the sample size were quadrupled?

Example 4

hard
If the confidence level is increased from 90% to 99% while the sample size and variability stay the same, what happens to the margin of error?
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