Sam Wang (Princeton): Why did the polls seem so variable this week? (more of them)

[muriel_volestrangler]

Why do the polls seem so variable this week? The basic answer is that there were a lot of them. Outliers are an inevitable consequence.
...
In this case, imagine that among pollsters, the standard deviation of the Clinton-Trump margin among pollsters is 3.5%. If there are 5 polls available, about half the time* one of them will be more than one standard deviation away from the median. Under current conditions, a typical range would be Clinton +2% to Clinton +9%.

With 17 polls available, the range will be more like 2.2 standard deviations in either direction. In that case the likely range is a whopping 16 points – Trump +2% to Clinton 14%. Which is just about what we saw this week.

Don’t be like journalists who run off after the most extreme report – that is ridiculous. The only honest thing to do is to take a median or average of all the polls you can get your hands on. Right now, the collected wisdom of all the poll is that Hillary Clinton is ahead by a median of 6 percentage points nationally. Not 4 points, and not 8 points. Her lead is 6.0 +/- 0.9 % (n=12 polls over the period October 20-26, median +/- estimated one-sigma standard error).

http://election.princeton.edu/2016/10/27/why-do-the-polls-seem-so-variable-this-week/

[DemonGoddess]

1. K&R!

[Wounded Bear]

2. In other words...don't panic...