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 2006

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 2006.