Calculate the margin of error for a sample estimate at a chosen confidence level.
How It Works
How Margin of Error Calculator Works
The margin of error combines how spread out your data is (standard deviation) with how large your sample is — larger samples shrink the margin of error, and higher confidence levels (which demand more certainty) widen it, since a critical z-value scales the whole calculation.
FAQ
Frequently Asked Questions
Why does a 99% confidence level give a wider margin than 95%?
Demanding more confidence that the true value falls within your range requires a wider net to catch it — the z-value used in the formula increases as the confidence level increases, directly widening the margin.
How much does doubling my sample size help?
Margin of error shrinks with the square root of sample size, not sample size directly — so doubling your sample only reduces the margin by a factor of about 1.41, not by half; you'd need roughly four times the sample to actually halve the margin.
