ebrown p wrote:
Regression lines are mathematical hocus-pocus. They should be mostly ignored. A regression line is a valid mathematical technique when the underlying data is linear (i.e. based on a function with a steady rate of change). As voter opinions are not even close to linear, a linear regression line is, mathematically speaking, a little more than useless.
Hm. OK. Well, since they only apply a linear regression trend line if they have between 4 and 7 polls, and this year pretty much any state (not to mention the national polls) had over 7 polls already many months ago, it's maybe not so relevant. I guess the two measures they specified for when there are less than 8 polls available were just stop-gap measures awaiting more polls, and those have become available a long time ago.
ebrown p wrote:
Let me inject a little math here. [..] As a former physics teacher I cringe when I see mathematically misleading graphs. Drawing a linear regression on non-linear data is unforgivable.
Hmm - well I sure as hell aint no expert, so I dont have anything to add here. But on a total sidenote -- irrelevant as this might be since this part of the methodology doesnt seem to be used in any of their current graphs anymore anyway -- I must admit to responding sceptically to this 'I am a former physics teacher and let me tell you, the system this guy is using is ****' stuff. I have this total flashback to Dr. Arzt, the high school science teacher in Lost
I guess I just mean, Charles Franklin, the guy who made it, is a Professor of political science at the University of Wisconsin, where he teaches statistical analysis of polls, public opinion and election results. He teaches graduate level statistics courses there and at Oxford, as well as at a University Summer School in Social Science Data Analysis. He's on the Special Committee on 2008 Presidential Primary Polling of the American Association for Public Opinion Research. Well, bla bla bla et cetera. All I know is he can go into excruciating detail about statistics and methodology when asked.
None of which means that everything he ever did must be foolproof or anything. Just that, well I guess if something strikes you straight away, I dunno, he's probably given it some thought too, and made the least worst choice available for a temporary status or something. Basically, since I have close to zero education in statistics myself, I just have to cast my lot with one or the other authority when there's a simple opposition of assertions that I dont have the expertise myself to check, and I feel pretty comfortable with him. But again, that just on an aside.