We would not dare use this term in sociology or anthropology now. (I know; I am a graduate in anthropology.) Anthropological and sociological observation is carried out under strict and demanding guidelines, certainly much more systematic than in Chesterton’s and Dr.Saleeby’s time; but we would not dream of calling our controlled observations “experiments”.

Just a small note of non-contradictory character: of course simple controlled observation is not an experiment, as you've said. This however does not exlude the possibility of using experiments in sociology or anthropology; this includes so-called "natural experiments", where the researcher do not actively manipulates the variables, but closely monitors (therefore controls) naturally occuring phenomena and changes happening under their influences.