AMERICANS'
KNOWLEDGE OF THE U.S. CONSTITUTION
A Columbia Law Survey
May 2002
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Conducted by
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Press Release
Fact Sheet
Vice Dean Michael Dorf's Columns About the Survey on FindLaw.com
"Americans' Knowledge of the U.S. Constitution"
A Columbia Law Survey
-CARAVAN Telephone Sampling Methodology
-Reliability of Survey Percentages
-Sampling Tolerances When Comparing Two Samples
-Introduction to Detailed Tabulations
-Detailed Tabulations (requires Adobe Acrobat)
SAMPLING TOLERANCES WHEN COMPARING TWO SAMPLES
Tolerances are also involved in the comparison of results from independent parts of any one Opinion Research Corporation's CARAVAN sample and in the comparison of results between two independent CARAVAN samples. A difference, in other words, must be of at least a certain number of percentage points to be considered statistically significant. The table below is a guide to the sampling tolerances in percentage points applicable to such comparisons, based on a 95% confidence level.
| Differences Required for Significance At or Near These Percentage Levels | |||||
| Size of Samples Compared | 10% or 90% | 20% or 80% | 30% or 70% | 40% or 60% | 50% |
| 1,000 and 1,000 | 3% | 4% | 4% | 4% | 4% |
| 1,000 and 500 | 3% | 4% | 5% | 5% | 5% |
| 1,000 and 250 | 4% | 6% | 6% | 7% | 7% |
| 1,000 and 100 | 6% | 8% | 9% | 10% | 10% |
| 500 and 500 | 4% | 5% | 6% | 6% | 6% |
| 500 and 250 | 5% | 6% | 7% | 7% | 8% |
| 500 and 100 | 6% | 9% | 10% | 11% | 11% |
| 250 and 250 | 5% | 7% | 8% | 9% | 9% |
| 250 and 100 | 7% | 9% | 11% | 11% | 12% |
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100 and 100 |
8% | 11% | 13% | 14% | 14% |