There are three columns in the figure. The column on the left has five boxes that indicate the relevant aspects of the intervention research, starting with Patients/Clients at the top, Practitioner(s), Setting, Treatment, and Outcome(s) on the bottom.
The middle and right columns have six boxes each. The top box in the center column, “Study reported,” has a dashed border rather than a solid line, to indicate it serves as a header for the five lower boxes, which are empty. The top box on the right-hand column, "Situation to which one wants to generalize," also has a dashed border rather than a solid line, similarly serving as a header for five lower boxes, all of which are empty. There is a large question mark between the two boxes that are headers for the center and right-hand columns. There is a doubled-headed arrow between each empty box in the middle column and the corresponding empty box in the right-hand column.