Mean value of the dependent is 0.053, 0.069 in rural sample, 0.035 in urban sample.
Trained interviewers selected households by random cluster sampling in urban (n=1,226) and rural (n=1,103) populations.
LOD and LOQ indicated possible application of these devices to sampling in urban intermediate, urban background and suburban areas.
Cluster sampling was based on block sampling in urban areas and family charts in rural areas.
Only the Mongolian, Hui, Uighur, Zhuang, and Korean minorities were sampled in urban and rural areas.
A uniform multistage sampling strategy was adopted in all states, with separate sampling in urban and rural areas.
Similarly, in Spain, the percentage of positive HAV samples in urban sewage fell from 57.4%to3.1%1% in 5 10 years, due to the general improvement in sanitation [ 20, 24].
Secondly, probability sampling in urban areas was conducted by selecting primary sampling units (blocks); then a sample of the required number of households was selected in each block with 800 to 1,000 households.
The control population of 50 subjects was sampled in urban areas of Peru: Trujillo (n = 42) and Lima (n = 4) on the coast, and Tarapoto city (n = 4), in the Amazon.
In Spain, studies from low endemicity areas revealed relatively low percentages of HAV-positive samples in urban wastewaters in recent years, ranging from 3.1% to 11% [ 13, 20], whereas studies from high/intermediate-endemicity areas yielded considerably higher percentages of HAV-positive sewage samples, up to 88% [ 21, 22].
