In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: Experimental factorial designs or also called complex experimental designs: 
 Options:  <1> They study the effect of an independent variable on several dependent variables. <2> They study the main effects of several independent variables and their possible joint effect or interaction. <3> They are inadequate if it is suspected that some of the study variables may have interaction effects. <4> They can dispense with experimental control techniques because of their complexity. <5> They are based on the application of all experimental conditions to the same group of participants.
2