Resources
Intro | Online Surveys | Qualitative Insights | Quantitative Insights | Facilities | Quality Management | Virtual Program Manager | Sample Estimator | Margin Of Error
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% |
|
