Table A-4.

Sampling errors (95 percent confidence level) for percentages estimated from the Gallup Poll: 1992, 1993, and 1996 through 2007

Percent	Size of sample
	1,500	1,000	750	600	400	200	100
Recommended allowance for sampling error of a percentage
Percentages near 10 or 90	2	2	3	3	4	5	8
Percentages near 20 or 80	3	3	4	4	5	7	10
Percentages near 30 or 70	3	4	4	5	6	8	12
Percentages near 40 or 60	3	4	5	5	6	9	12
Percentages near 50	3	4	5	5	6	9	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 2007.