- If you use the sample proportion (p) from a simple random sample of size n to estimate an unknown population proportion p, then the margin or error for 95% confidence is roughly equal to 1 divided by the square root of n.
- For example, if I say "margin of error plus or minus 3 percentage points: is shorthand for this statement:
- If we took many samples using the same method we used to get this one sample, 95% of the samples would give a result within plus or minus 3 percentage points of the truth about the population.
- A confidence statement has two parts: a margin of error and a level of confidence. The margin of error says how close the sample statistic lies to the population parameter. The level of confidence says what percent of all possible samples satisfy the margin of error.
What is the margin of error?
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