Hi All,<p>What do you all think about the validity of Alexa rankings? Is it your opinion that the stats that they produce are an accurate representation of users, or is it likely a more techie demographic?<p>Would you use the stats for talking to potential online advertisers?<p>Thanks!
Alexa users are a convenience sample, not a simple random sample, and they may badly misrepresent your user base. Essentially, installing Alexa (which I did once, but haven't done on my current browser) is something like participating in a voluntary response poll. One professor of statistics, who is a co-author of a highly regarded AP statistics textbook, has tried to popularize the phrase that "voluntary response data are worthless" to go along with the phrase "correlation does not imply causation." Other statistics teachers are gradually picking up this phrase.<p>[quote=Paul Velleman]<p>-----Original Message-----
From: Paul Velleman [SMTPfv2@cornell.edu]
Sent: Wednesday, January 14, 1998 5:10 PM
To: apstat-l@etc.bc.ca; Kim Robinson
Cc: mmbalach@mtu.edu
Subject: Re: qualtiative study<p>Sorry Kim, but it just aint so. Voluntary response data are <i>worthless</i>. One excellent example is the books by Shere Hite. She collected many responses from biased lists with voluntary response and drew conclusions that are roundly contradicted by all responsible studies. She claimed to be doing only qualitative work, but what she got was just plain garbage. Another famous example is the Literary Digest "poll". All you learn from voluntary response is what is said by those who choose to respond. Unless the respondents are a substantially large fraction of the population, they are very likely to be a biased -- possibly a very biased -- subset. Anecdotes tell you nothing at all about the state of the world. They can't be "used only as a description" because they describe nothing but themselves.[/quote]<p><a href="http://mathforum.org/kb/thread.jspa?threadID=194473&tstart=36420" rel="nofollow">http://mathforum.org/kb/thread.jspa?threadID=194473&tsta...</a><p>But to answer your underlying question, if I had good Alexa stats, I would talk them up. You may as well talk about the most convincing data you have, while acknowledging that the data may not be definitive.
I typically utilize Alexa and Compete or others as a good way to compare sites of a similar demographic. Having access to google analytics for two different sites; one being my blog and the other site is the company I work at.<p>I know that my blog gets about half the traffic of my companies site but the corporate site is ranked 370,673 and my blog is ranked 395,487. I would think there would be more of a difference in the two sites ranking.<p>But if I compare several of our companies competitors sites the numbers seem to line up. The numbers also make sense as trend data for a single site. I know from monitoring my blog when there is a spike in traffic; Compete and Alexa show a spike in their rankings.<p>Because Alexa captures their information through a browser plugin you want to make sure that the set of people that visit each site are equally likely to have the plugin installed. If people that read hacker news are half as likely to install the Alexa Plugin then people that read the new york times then there would be variability in comparing those two site.
I think all 'free' online ranking sites give you data that you should take with a large grain of salt. You can use some of them for relative comparisons but not if the comparison is a close one.<p>Another use is to extrapolate from 'known' numbers to an unknown site (say a competitor).<p>It helps to separate truth from bull, but it is definitely not an exact measurement. If someone is off by a factor of 10 then you're on solid ground to call bull, if it is a factor of 2 or less then it gets a lot harder.