Pollster Guru Nate Silver's Forecasts of GOP Gains Has Bizzare Margin of Error

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from Nate Silver on the NYT FiveThirtyEight blog: http://fivethirtyeight.blogs.nytimes.com/2010/10/10/number-of-competitive-house-races-doubles-from-recent-years/?hp


The House forecast that we released on Friday establishes an over-under line for Republican gains at a net of 47 or 48 seats. But, as I noted at the end of the article, the confidence interval on this forecast is very wide. Its margin of error is about ±30 seats — meaning that a gain of as few as 17 seats, or as many as 78, is entirely possible — and there is a small chance of even larger or smaller gains.

When I noted this on Twitter on Friday, I got a few sarcastic replies: what good is a forecast if it tells you that essentially anything can happen . . .?

____ According to just about every objective and subjective indicator, then, the number of competitive House districts is roughly twice as high as in recent years. This is why the margin of error on our House forecast is very wide. If the polling is off by just a little in one direction or another, it could have profound consequences for the number of seats that Republicans are likely to gain. Likewise, there are a great number of districts in which both parties have viable candidates who could overperform or underperform the trends present in the national environment . . .


read more: http://fivethirtyeight.blogs.nytimes.com/2010/10/10/number-of-competitive-house-races-doubles-from-recent-years/?hp