Français
Margin Of Error
The margin of error for any survey based on a random sample depends on both the size of the sample and the observed proportion. The table below contains the margins of error (at a 95% confidence interval) for sample sizes that vary from 100 to 4000 and for observed proportions that range from 10% to 90%. For example, the margin of error for a survey of 1000, where the observed proportion is 50% is ±3.1%. This means the true proportion is between 46.9% and 53.1%, 19 times out of 20.
| MARGIN OF ERROR Sample Size |
|||||||||||||
| Observed Proportion | 100 | 200 | 300 | 400 | 500 | 700 | 1000 | 1500 | 2000 | 2500 | 3000 | 3500 | 4000 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ± | ± | ± | ± | ± | ± | ± | ± | ± | ± | ± | ± | ± | |
| 10% or 90% | 5.9% | 4.2% | 3.4% | 2.9% | 2.6% | 2.2% | 1.9% | 1.5% | 1.3% | 1.2% | 1.1% | 1.0% | 0.9% |
| 20% or 80% | 7.8% | 5.6% | 4.6% | 3.9% | 3.5% | 3.0% | 2.5% | 2.0% | 1.8% | 1.6% | 1.4% | 1.3% | 1.2% |
| 30% or 70% | 9.0% | 6.4% | 5.2% | 4.5% | 4.0% | 3.4% | 2.8% | 2.3% | 2.0% | 1.8% | 1.6% | 1.5% | 1.4% |
| 40% or 60% | 9.6% | 6.8% | 5.6% | 4.8% | 4.3% | 3.6% | 3.0% | 2.5% | 2.2% | 2.0% | 1.8% | 1.6% | 1.5% |
| 50% | 9.8% | 6.9% | 5.7% | 4.9% | 4.4% | 3.7% | 3.1% | 2.5% | 2.2% | 2.0% | 1.8% | 1.7% | 1.6% |