(17KB)| Table A-5. | Table A-5. Sampling errors (95 percent confidence level) for the difference in two percentages estimated from the Gallup Poll: 1992, 1993, and 1996 through 2008 |
| Size of first sample | Size of second sample | |||||
| 1,500 | 1,000 | 750 | 600 | 400 | 200 | |
| Recommended allowance for sampling error of a difference in percentages (percentages near 80 or 20) | ||||||
| 1,500 | 4 | 4 | 5 | 5 | 6 | 8 |
| 1,000 | 4 | 5 | 5 | 5 | 6 | 8 |
| 750 | 5 | 5 | 5 | 6 | 6 | 8 |
| 600 | 5 | 5 | 6 | 6 | 7 | 8 |
| 400 | 6 | 6 | 6 | 7 | 7 | 9 |
| 200 | 8 | 8 | 8 | 8 | 9 | 10 |
| Recommended allowance for sampling error of a difference in percentages (percentages near 50) | ||||||
| 1,500 | 5 | 5 | 6 | 6 | 7 | 10 |
| 1,000 | 5 | 6 | 6 | 7 | 8 | 10 |
| 750 | 6 | 6 | 7 | 7 | 8 | 10 |
| 600 | 6 | 7 | 7 | 7 | 8 | 10 |
| 400 | 7 | 8 | 8 | 8 | 9 | 11 |
| 200 | 10 | 10 | 10 | 10 | 11 | 13 |
| SOURCE: Phi Delta Kappa, Phi Delta Kappan, "The Annual Gallup Poll of the Public's Attitudes Toward the Public Schools," 1992, 1993, and 1996 through 2008. |