On Thu, 07 Apr 2011 12:49:34 EDT, [email protected] said: > If we take 100 people on this list, have them all look in their backyards and > report if there is any paper or plastic blowing around, I'll bet we can come > up > with a fairly high percentage of us that don't have any paper or plastic > blowing around. I'll further say that I'll bet the number would be within a > standard deviation of 4% error. So, if 96% of us don't have any paper or > plastic blowing around in our yards, could we safely say that no-one litters?
No, you can safely say that the population average of litter-free backyards is has a 70% chance between 92% and 100%, and about 95% chance of being between 88% and 100%. (Yes, it's likely to be closer to a chi-squared curve than a gaussian bell curve due to the constraint of one tail). The problem is that careful analysis is needed - I'll make a prediction that yards with chain link fences have a lot higher level of wind-born litter than unfenced yards. This of course impacts your analysis of litter sources. And incidentally, Rick *has* done the "take 100 people" type analysis, which is why he commented that (basically) the plural of anecdote isn't data.
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