т.е. "a nationally representative sample" означает что? или выборка репрезентативная, а опрос нет?Methodology
From the September 14, 2007 ORB press release[1] concerning the first set of interviews:
Results are based on face-to-face interviews amongst a nationally representative sample of 1,720 adults aged 18+ throughout Iraq (1,499 agreed to answer the question on household deaths)
The standard margin of error on the sample who answered (1,499) is +2.5%
The methodology uses multi-stage random probability sampling and covers fifteen of the eighteen governorates within Iraq. For security reasons Karbala and Al Anbar were not included. Irbil was excluded as the authorities refused the field team a permit.








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