[xiphias]

Thanks for the answer. When I was implementing a language learning program (who hasn't? :) ), using logistic regression was working quite well to quickly find my vocabulary level in about 10 questions in the top 10000 most frequently used words list adaptively (I ran a full logistic regression on the user dataset after each new data point, by mapping the position of the words to the estimated level of the user), and the questions just felt right. So I'm not talking about multiple logistic regression model, just using 1 variable, which works with lots of questions (as long as the question hardness is well calibrated).

Although I'm happy that you're trying to predict the most informative question, for me some questions near the end felt trivial, so either my feeling wasn't right about the hardness of a question, or the algorithm has lots of space to improve, or the question hardness levels weren't calibrated optimally.

Anyways congrats for the success for your startup (I just hope that you prioritize people who don't have U.S. VISA)!