I am, after all, in education, and not all that long ago we used to talk about "distance learning", and one of the hot topics was whether the outcomes for students enrolled in "correspondence courses" were as good as those in "traditional" classrooms. Thomas L. Russell from North Carolina State University collected a vast number of studies that showed ... "no significant difference" between the two. This led to a book, and a web site with that name, and established the often cited meme of that same name. Frankly, I don't remember when I last saw a reference to the phenomenon (which shouldn't be particularly surprising considering that when internet-based teaching pushed "distance learning" aside it also started reinventing education from scratch and had no interest in what might have been happening in the pre-internet dark ages) but I'm sure that for anyone who was connected in any way to educational research in the early 1990s, and for quite a while after that, the phrase "no significant difference" immediately brings back memories.