Sunday, May 31, 2009

Statistics class:

Balloon Juice has flagged this blog post about a possible conspiracy to help Chrysler dealers who donated to Clinton:
This puzzled us. Why would there be a significant and highly positive correlation between dealer survival and Clinton donors? Granted, that P-Value (0.125) isn’t enough to reject the null hypothesis at 95% confidence intervals (our null hypothesis being that the effect is due to random chance), but a 12.5% chance of a Type I error in rejecting a null hypothesis (false rejection of a true hypothesis) is at least eyebrow raising. Most statistians would not call this a “find” as 95% confidence intervals are the gold standard for this sort of work. Nevertheless, it seems clear that something is going on here. Specifically, the somewhat low probability that the Clinton data showing higher survivability of Clinton donors could result just from pure chance. But why not better significance with any of the other variables? Why this stand out?
What's that all about, you might ask. Well, it turns out that Wikipedia's entry for p-value contains an example with almost the same value (.115). Turns out .125 isn't all that remarkable at all.


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