Your message is not related to my post, and a good indication is that
the given quote is incomplete even for the purpose of making the point
of that particular experiment.  

If you don't believe that 1 to 1 tuition is a help learning a language, then why did you provide it? What's the point of lists like this where people can ask questions? Of course it is a help!
 
Then that point alone is also not enough
either, because there is a strong connection between the two examples I
mentioned.  

There would be a "strong connection" if each individual in the group got as much time as your friend did and this time was provided to them in the same way as she received it, motivation was the same, etc. But this isn't what you said!

 
All in all you apparently didn't understand a word of my
post.

Obviously I disagree: I think that I understood what you wrote and found it unconvincing:

-You can't conclude that because two groups are differentiated by property X (in this case previous programming experience, with lack of it being more favourable to learning Haskell) then property X is responsible when the outcome of a test procedure is different. ***Not unless the test procedure is the same and those groups are the same.***

Which wasn't the case, not nearly. Individual tuition over a time is an ideal way to learn a language, while short taught courses are an utter waste of time - a decent book is better.

Concluding that differences in outcome *had* due to be due to anything else than the different methods in teaching, time spent, motivation, relationship with the students, etc, is... well, if this was a science paper you'd be getting a fail grade. There are so many factors here that you haven't controlled for that it is silly. There are probably creationists and global warming deniers who would be shocked at your selecting the answer that you want from a host of possible ones. You've picked X, but Y, Z, U, A, B and Alpha were all possible!

But all this is moot - the guy isn't learning to program for fun but for a purpose. Sagemath and R have the libraries and R in particular seems to be a lingua franca in econometrics and time series analysis, which are probably relevant. Haskell would be a poorer tool in this area than R, simply because knowing it wouldn't allow the guy to read useful papers. Then there are libraries to consider...