Glad that you did, Sarah!

     Eddie, nice of you to share the site, very kind of you.

     By the way, when it comes to tests, I have never seen them explained before...I mean, how they designed the test itself. 

     This one has this area  http://testyourvocab.com/about.php wich explains who devised the so called "tool".    

      So, "TestYourVocab.com is part of an independent American-Brazilian research project to measure vocabulary sizes according to age and education, and particularly to compare native learning rates with foreign language classroom learning rates."     Very interesting indeed, I am proud of it! hehe.

    Crawling within  http://testyourvocab.com/details.php  I learned that:

You may ask—is it really necessary to exclude so many words? Shouldn't being able to figure out "unhappy" count as knowing the word? Well, this brings us to a final distinction: receptive vocabulary (the words we understand, but don't/can't use) versus productive vocabulary (the words we use in speaking and writing).
Our receptive vocabulary is significantly larger than our productive vocabulary. In many ways, it acts as a "multiple" of our productive vocabulary, allowing us to recognize more words based on the words we already know. However, if we simply included all words we understand, we run the risk of an English speaker who has never heard a word of Spanish before, testing that he "knows" perhaps tens of thousands of Spanish words!       ... And because we're using the same vocabulary list to test Brazilians learning English...

    Nice concepts, these ones of receptive and productive vocabulary!