Sampling & Margin of Error
A sample can estimate a population. The margin of error shows the likely range.
The rules
- A random sample is more reliable than a convenience sample.
- A larger sample gives a smaller margin of error.
- An estimate of 50% ± 3% means the true value is likely between 47% and 53%.
- Be careful about claims that go beyond the population sampled.
Watch out: Generalizing to a group the sample doesn't represent.
Worked example
A poll finds 52% support with a margin of error of ±4%. What is the likely range?
- 52 − 4 = 48.
- 52 + 4 = 56.
Answer: 48% to 56%
Try it yourself
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