Question Z LS 1b. What is one obvious source of confounding that threatens the article's conclusion that online learning is no less effective than face-to-face learning? O Students got to self-select; that is to decide for themselves which course (online or faceto- face) they enrolled in. O Students were not able to decide for themselves which course (online or face-to-face) they enrolled in. There were significantly more males in the online class than in the face-to-face class. The pre-test scores of the two groups were identical, making it virtually impossible to say one type of class was better than the other