Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
C-1 Appendix C â Samples Required in Representative Surveys The following table summarizes the number of samples required (e.g., completed surveys) assuming random selection to achieve a certain confidence level for a given population size. To use the table, identify the overall population size on the left-hand column, and then select the column with the desired confidence interval to determine the required number of samples. For example, for a population of 500 and a desired confidence interval of ±5%, 217 completed surveys are required assuming random selection. Table 8. Number of Completed Surveys Required Assuming Random Selection Population Size Confidence Interval (at 95% confidence level) ±10% ±7% ±5% ±3% 25 20 22 24 24 50 33 40 44 48 75 42 54 63 70 100 49 66 80 92 150 59 85 108 132 200 65 99 132 169 300 73 119 169 234 500 81 141 217 341 1,000 88 164 278 516 1,500 90 173 306 624 2,000 92 179 322 696 3,000 93 184 341 787 5,000 94 189 357 880 10,000 95 192 370 964 20,000 96 194 377 1013 40,000 96 195 381 1039 80,000 96 196 382 1053 160,000 96 196 383 1060 300,000 96 196 384 1063 600,000 96 196 384 1065 1,000,000 96 196 384 1066