Cracking the Muhlenberg Code

Why do the polling firms conducting daily tracking polls not release the results of the individual days along with the rolling averages they are producing? Ah, wouldn't it be nice. In reality, they don't and that leaves people like me wondering about how to go about determining what those numbers are. As the good folks at FiveThirtyEight showed, however, it is an inexact science that just has too many unknowns to definitively determine that data. What they looked at was the national trackers. But what I'm more interested in are the state level daily trackers. We only have one so far and it is the poll conducted by the Institute of Public Opinion at Muhlenberg College along with Morning Call. So, what do we know and what don't we know?

[Click Figure to Enlarge]

Above you'll see, from the Institute itself, the results from each of the first six days of the tracking poll in question. Now, to keep things simple, we'll focus just on margins and not each candidate's percentage. The latter just replaces one unknown with two more and that muddies the picture that much more. What we see, though, is that the margin increases by one for each of the first five days of the five day rolling average. That tells us that for each of those days the new data coming into the average (an additional days worth of data) has a margin that is about five points greater than the day that is being subtracted from the rolling average.

Huh? How do you know that? Well, each new release has five different days worth of polling. For instance the first release last Friday found that between the dates of September 21 and September 25 Obama averaged a four point lead over McCain. We know that the sum total of those five polls is somewhere around 20 (5 polls X 4 point margin). [I continue to say "around" because we are dealing with rounded numbers here. Again, that is another way in which this examination is oversimplified, but it is the information we have available to us.] If the average increases to five, then we know that that total increases to 25 (5 polls X 5 point margin). And as that one point increase pattern continues, you simply add five more points to the average until things either level off or drop.

If we assume that each of those days in the first poll released last Friday had the exact same result, then we would see something like this:

Muhlenberg Tracking Polls - PA (Oct. 1): Scenario #1
	Date
Polls	21	22	23	24	25	26	27	28	29	30
#1	4	4	4	4	4
#2		4	4	4	4	9
#3			4	4	4	9	9
#4				4	4	9	9	9
#5					4	9	9	9	9
#6						9	9	9	9	-1

So if every day in the original poll found Obama to be up four, he would have to be up nine on the sixth day when the first day's four point margin is phased out. We can continue that replacement and it looks just fine until you get to yesterday's poll, when the margin dropped by one. Not only does the above hypothetical assume things into simpliticity, it is also probably unrealistic. I think it is unlikely that there was a McCain blip in there, as the -1 would imply.

It is not unrealistic, then, to forcibly constrain things to the Obama side of the ledger. But what that tell us is that, if the original average was four points and if there was a drop in the margin yesterday, then there must have been an inflated number on the last day (September 25) of the initial poll. That would be the day that was phased out in the data that the Institute released yesterday. To frame this slightly differently, there was likely something of an established pattern to the data from September 21-24, but the data from the 25th was a significant departure from that pattern, one that altered things thereafter. Below, I think, is a good guess as to how things may have looked over the course of the first ten days of the tracking poll.

Muhlenberg Tracking Polls - PA (Oct. 1): Scenario #2
	Date
Polls	21	22	23	24	25	26	27	28	29	30
#1	2	3	2	3	10
#2		3	2	2	10	7
#3			2	3	10	7	8
#4				3	10	7	8	7
#5					10	7	8	7	8
#6						7	8	7	8	5

We know that since there was a one point drop in the margin yesterday, that there was around a five point drop in the total of all five days' polls. When we additionally factor in the fact that there was a drop, but one that still showed a pretty good lead for Obama, you get a pattern similar to what is depicted above. Things were close and then, suddenly, they weren't.

Is this right? I don't know. As I said this is just a guess. More importantly, how is FHQ going to deal with the data from Muhlenberg? We are, like what is being done at Electoral-Vote.com, going to take one poll every six days. That way no one day in this series of surveys is being counted more than once. The first poll Muhlenberg released covered September 21-25. We would take that poll and then the one where the 25th is phased out of the average (the poll covering September 26-30). That decision was reflected in last night's update of the map.


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