LAWYERS
AND THE LEGAL PROFESSION
A Columbia Law Survey
April 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
"Lawyers and the Legal Profession"
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)
RELIABILITY OF SURVEY PERCENTAGES
Results of any sample are subject to sampling variation. The magnitude of the
variation is measurable and is affected by the number of interviews and the
level of the percentages expressing the results.
The table below shows the possible sample variation that applies to percentage
results reported from Opinion Research Corporation's CARAVAN sample. The chances
are 95 in 100 that a CARAVAN survey result does not vary, plus or minus, by more
than the indicated number of percentage points from the result that would be
obtained if interviews had been conducted with all persons in the universe
represented by the sample.
|
Size of Sample on |
Approximate Sampling
Tolerances Applicable to Percentages At or Near These Levels |
|||||
| 10% or 90% | 20% or 80% | 30% or 70% | 40% or 60% | 50% |
||
| 2,000 interviews | 1% | 2% | 2% | 2% | 2% | |
| 1,000 interviews | 2% | 2% | 3% | 3% | 3% | |
| 500 interviews | 3% | 4% | 4% | 4% | 4% | |
| 250 interviews | 4% | 5% | 6% | 6% | 6% | |
| 100 interviews | 6% | 8% | 9% | 10% | 10% | |
| Additional Sampling Tolerances for Samples of 1,000 Interviews | ||||
| 9% or 91% 2% |
8% or 92% 2% |
7% or 93% 2% |
6% or 94% 1% |
5% or 95% 1% |
| 4% or 96% 1% |
3% or 97% 1% |
2% or 98% 1% |
1%
or 99% .2% |
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