CAMPBELL’S AND STANLEY’S SYMBOLIC REPRESENTATION OF ‘TRUE’ EXPERIMENTS RO1 X O2 RO3 O4 Campbell, D. T. and Stanley, J (1963) Experimental and Quasi-experimental Designs for Research on Teaching. Boston: Houghton Mifflin Co.
CAMPBELL’S AND STANLEY’S NOTATION X represents the exposure of a group to an experimental variable or event, the effects of which are to be measured. O refers to the process of observation or measurement. Xs and Os in a given row are applied to the same persons. Left to right order indicates temporal sequence. Xs and Os vertical to one another are simultaneous. R indicates random assignment to separate treatment groups. Parallel rows unseparated by dashes represent comparison groups equated by randomization, while those separated by a dashed line represent groups not equated by random assignment.