They were each at pains to point out that it is a mistake to read too much into one month's figures, or one individual survey.
Even though the Iowa Poll has a good record, it is best not to place too much stress on any individual survey, especially when it is indicating, as this one does, that the races are tight.
At this late stage of the campaign, practically all of the models rely very heavily on polling data, with the main differences being what weights they attach to each individual survey.
Equally, the Halifax data looks like an extreme generated by a sampling error – the volumes of properties bought and sold each month have fallen to such lows that each individual survey is no longer necessarily a representative sample.
The individual survey weights were generated separately for adults and children.
We aimed to address this bias by guaranteeing anonymity and confidentiality of all individual survey data.
Of these, between 38 and 44 participants responded to individual survey items.
NGT is a highly structured technique combining characteristics of an individual survey and a focus group.
"The ice thickness model alone uses 25 million individual survey points," he told BBC News.
The NGT is a highly structured technique with characteristics of an individual survey and a focus group.
This paper is based on individual survey data and data about household economy from the household questionnaire.
