538's take on the Disparity between polls like CNN/SSRS and Quinnipiac.

[UncleNoel]

This issue has cropped up here a number of time vis-à-vis Biden Friendly and Warren friendly polls.

https://fivethirtyeight.com/features/biden-up-15-warren-up-7-are-primary-polls-too-far-apart/?ex_cid=2020-tracker
Oct. 31, 2019, at 5:58 AM
Biden Up 15. Warren Up 7. Are Primary Polls Too Far Apart?
By Laura Bronner

Last week, two polls painted two very different pictures of the state of the primary race. A CNN/SSRS poll put former Vice President Joe Biden 15 points ahead of Sen. Elizabeth Warren, 34 percent to 19 percent, while a Quinnipiac University poll released a day later found Biden trailing Warren by 7 points, 21 to 28 percent.

As both The New York Times and The Washington Post pointed out, these are pretty large discrepancies for two polls in the field at roughly the same time (the CNN poll was in the field from Oct. 17-20, the Quinnipiac poll from Oct. 17-21). But trying to figure out which poll is more accurate is kind of beside the point. After all, these are only two polls of a primary that has been polled hundreds of times, and it isn’t necessarily a problem that two pollsters arrived at different conclusions.

In analyzing October polls, it was found that the random sampling variability and found by analyzing all national Democratic primary polls for October that "the spread between all the October polls is way outside the range of standard deviations for what we would expect — for both Biden and Warren." (See link for chart).

That suggests that it isn’t just sampling error that’s driving the differences we’re seeing — it implies there are some real methodological differences between the polls. Pollsters regularly use different approaches to polling, sampling and weighting, which can often lead to different outcomes. This is actually a good thing, since there’s a lot of uncertainty about the electorate in 2020 and it’s important that different pollsters make independent decisions about how to analyze it. This is why it’s important to control for variations in pollsters’ techniques when analyzing individual polls. Each pollster’s preferred methodology tends to make its results lean a little toward one party or to certain candidates — these leans are commonly known as “house effects,” and they can help explain some of the variation we’re seeing.

Adjusting fr "house effects" they found that
o

...this tell us about those CNN and Quinnipiac polls? In short, the fact that they found such different outcomes isn’t that big a deal. As you can see in the chart below, once we control for house effects, the overall spread between polls since May isn’t actually all that large. In fact, the spread of values for both Biden and Warren fall within a range we might expect. So don’t read too much into those two polls. Turns out they’re just the kind of outliers we’d expect to see in this range of polls.

Very interesting. And to conclude on a high note, they provided a char"t to put thee two polls in perspective in ration to of all national polls for Biden and Harris since May 2019 "adjusted for House effects" and taking sample size into consideration..



I find this to be a very intriguing chart of Biden's and Warren's trajectories. Aside from the issue of the two mentioned polls, all the poll averages show Biden showing a long pretty steady course and Warren surging and then slipping a bit near the end of October. Pretty much like my Corps d'Elite poll showed (new version up when the last of the October polls show up).

[SterlingPound]

1. America

loves mediocrity.

[Demsrule86]

4. Are you calling Biden mediocre? He is not such thing.

[DownriverDem]

7. Not only that

Biden can win the Electoral College and beat trump.

[Demsrule86]

11. Yep, he is the only one that can take the states we need IMHO.

[SterlingPound]

13. So can every other Dem Running IMO

[SterlingPound]

14. I can't say that he is without sounding like i am attacking him

i will vote for Joe if he gets the Nomination but He is the Avatar of Mediocrity and will not advance this country at all for 4 more years


we Can DO BETTER

[Celerity]

5. Da faq?

[sarisataka]

6. If you look under

The next bridge you cross I believe you will find the usual resident is missing

[Demsrule86]

3. Warren supporting pollsters...methodology amounts to finger on the scale.

[jcgoldie]

8. Except that you show absolutely zero evidence about methodology

Your only problem seems to be with the results.

[Act_of_Reparation]

9. We don't even know what methodology they used.

But apparently we know it's wrong. Because reasons.

[Demsrule86]

10. The methodology was discussed in the OP. Wyhy should I show anything...there is no question in my

mind that some polls tilt towards Warren because they support her. It is an opinon. Take it for what it is worth...and I have looked at methods and sample size...the questions asked in numerous polls actually...I believed it before this OP...for example some polls picked voters that were not even Democrats...or were not registered for anything. There are all sorts of ways to skew the results...I guess we will see in the end who is correct.

[jcgoldie]

12. No question in your mind

Got it!