This Hattie-interview by Hanne Knudsen is very interesting although I think some statisticians will frown if they read the quote used as title “I’m a statistician, I’m not a theoretician”.

It advice to read the full article, but this excerpt explains the quote more in dept:

…if I had known that it would go to an audience larger than just researchers, I probably would have had a whole lot more of theory in it. I had never dreamed it would catch on like this, so you are right, it is quite devoid of theory in terms of how it is written. I am a measurement researcher, I am a statistician, I am not a theoretician, so I haven’t written a lot of theory. But of course I have a very strong model of teaching. I have worked for many years with some of the more well-known people on the theoretical side of teaching around the world. But you are right, it did not come through, and sometimes I think I should write a book about teaching as a profession – which indeed I am doing right now. I get accused more of not taking into account sociology, and the background of kids. Of course I think that is very critical, but the book was never written for that kind of general notion. You are right, it is a criticism, and maybe I should write something more theoretical, but it is not really my strength. I do have some very strong theories on how theory works and the concept of teaching. It just didn’t come through in the book