Personally I don't know why you did an experiment. If you have a toolbar and visit your site you are bound to increase your rankings. Alexa is inaccurate and always has been, but they are still good to use for some things.
Even i don't consider the Alexa ranking as it only counts the hit of those machine which have alexa toolbar. it is not at all usefull. Even I have read so many articles about the same.
Personally, once I found that all of their data came from the toolbar alone their importance plummeted. Maybe they will improve by partnering with another algorithm.
I love seeing postings of people who put great value on Alexa Ranking as a determiner for buying, or the price of a domain. It's like watching a puppy that has seen his reflexion in the mirror for the first time.
People on this very forum are selling 10k hits by a bot using proxies to boost their alexa ranking which they claim will encourage frequent search engine spider visits. Even I, when buying traffic, I check their alexa ranking even though I know its not 100% accurate. its reputation proceeds it.
I've never put any worth in Alexa - its not a widely used tool since your ranking and the "success" it implies is largely dependent on Alexa's own success in spreading their plugin around the net. I guess for someone who really wants to look at it in depth it could be interpreted comparatively, but... meh...