Margin of Error
The margin of error to be allowed for in any estimate depends mainly on the number of interviews on which it is based. Margin of error gives indications of the likely range within which estimates would be 95% likely to fall, expressed as the number of percentage points above or below the actual estimate. Allowance for design effects (such as stratification and weighting) should be made as appropriate.
| Sample Size | Percentage Estimate |
| 40% – 60% | 25% or 75% | 10% or 90% | 5% or 95% | |
| 1,000 | ±3.0 | ±2.7 | ±1.9 | ±1.3 |
| 5,000 | ±1.4 | ±1.2 | ±0.8 | ±0.6 |
| 7,500 | ±1.1 | ±1.0 | ±0.7 | ±0.5 |
| 10,000 | ±1.0 | ±0.9 | ±0.6 | ±0.4 |
| 20,000 | ±0.7 | ±0.6 | ±0.4 | ±0.3 |
| 50,000 | ±0.4 | ±0.4 | ±0.3 | ±0.2 |
