On Iowa and ARG

08/01/2007 04:30 am ET | Updated May 25, 2011

The release of new

yesterday by the American

Research Group
(ARG) in Iowa, New Hampshire and South Carolina has

generated quite a bit of buzz as well as questions about ARG of the sort I

alluded to yesterday in my post on the screens pollsters use to select likely primary

voters and caucus attendees. That post is the first in a series that will look

at the methodological differences among the various pollsters active in the

early primary states. For now, however, let me take up two issues specific to Iowa and ARG's surveys


The first question comes from reader AL:


think your averaging is wrong on the Iowa

race for the democrats. I think it should be Edwards at 25.7 and Hillary at

25.4. You have the averaging mixed up. You should correct it.

I am not sure how AL arrived

at those numbers, but the current estimates in Iowa (Clinton 25.7%,

Edwards 25.4%) are not "mixed up." The confusion may arise from the fact that

our estimates are regression based estimators rather than true averages. Professor

Franklin explains the difference in detail here.


The second issue concerns the Iowa

surveys by ARG.

As commenter jsamuel put

, "ARG seems to almost always under poll Edwards." While I lack Professor

Franklin's flair for graphics and regression trend lines, some simple averages show

that jsamuel is right. Sen. Clinton does consistently better ARG's surveys than

those from other pollsters, while former Sen. Edwards does consistently worse:


We logged in six new Iowa

surveys during June and July. The two from ARG show Clinton ahead of Edwards by an average six

points (31% to 25%), while the four from other pollsters give Edwards an

average lead of five points (27% to 22%).

Surveys from February, March, April and May show essentially the same

pattern. Clinton

leads by two points (30% to 28%) in four surveys conducted by ARG, while

Edwards leads by an average six points (27% to 21%) in 13 surveys by other


Unfortunately, this is the sort of scenario in which

averaging (or simple regression based estimation) can be potentially

misleading. One pollster (ARG) is getting consistently different results and contributing a large number of polls

to our overall estimate. So if ARG is both different and wrong, their polls are throwing off our estimates.

We know ARG's results in Iowa are different. Why? And what should we

make of that difference? For some clues, stay tuned to my series on primary



Iowa Pollster