Does the study sample accurately represent the Iraqi population?
The requirement for a sample that accurately representats the Iraqi population essentially is that all members of the population have an equal chance of being included in the sample. If this is the case, the sample is said to be “random”, which in turns allows standard statistical techniques to be used for inferences about overall mortality. The Lancet article contains a compressed discussion of the method by which the sample was constructed for the mortality study:(p. 2): • 50 clusters were selected systematically by Governorate with a population proportional to size approach, on the basis of the 2004 UNDP/Iraqi Ministry of Planning population estimates. • Each Governorate’s constituent administrative units were listed by population or estimated population, and location(s) were selected randomly proportionate to population size. • A main street was randomly selected within the administrative unit from a list of all main streets. • A residential street was then randomly selected from a
