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Originally Posted by babsy
Alexa only really works for people who have installed the Alexa toolbar. It's not an absolutely realistic figure, although it's entirely possible they're guessing the percentage of people on the planet who have installed their software and then multiplying by that.
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Babsy,
You're correct, but Alexa has it's toolbar on enough machines that it can predict accurately within a 95% confidence interval (stats talk, sorry) that the numbers are correct. It's kind of like the election polling statistics. They don't poll the whole country, just enough to make their results statistically accurate.
In one given day, variations could cause it to over or under-report numbers, but if you look at weekly/monthly averages it should be a representative number.
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