Reply #19: I just tried to email ESI [View All]

[Febble]

but failed. It might be necessary to register first, but I can't because it won't accept my British Zip code.

Here is what I wrote:

I have a query about your Ohio study. When you give the limits of the possible ranges of WPE that can be due to non-response bias, I have been assuming that this is computed by postulating, in turn, that all non-responders voted for Bush, and all non-responders voted for Kerry. And by "non-responders" I am assuming that you mean those selected for interview and either "missed" (interviewer busy) or who refused. However, it is presumably possible that another form of non-response bias could occur, beyond your limits, if the actual sampling process was biased. An interviewer who tended to select friendly looking faces might end up with a high completion rate, a narrow pair of limits on his/her "possible" WPE, but a WPE beyond those limits because, say, the friendlier faces tended to belong to Kerry voters.

However I may have misunderstood the nature of your limits. It seems to me that "non-response bias" can operate at the level of literal "non-response" but also at the level of voter selection. Bush voters may have had a greater rate of "non-responding" not because they refused or were "missed" (and recorded missed) but because they, for one reason or another, tended to escape selection.

In which case, unless I have misunderstood your definition, your two "impossible" precincts are explicable in terms of slightly broader definition of non-response bias. I would be grateful if someone could clarify this as I am frequently asked about it.

Elizabeth Liddle


If you'd like to try and send it yourself, I'd like to know the answer!