The core strength of an alternating treatment design ATD also known as a multielement design is its ability to rapidly compare the effects of two or more independent variables interventions by alternating them within the same experimental phase However this rapid alternation makes the ATD highly susceptible to carryover effects multiple treatment interference or sequence effects Carryover effects occur when the effects of one treatment condition persist and influence the participants behavior during a subsequent treatment condition If one communication prompting strategys impact eg a specific prompt fading schedule or a reinforced response affects how the client responds to a different prompting strategy introduced immediately afterward the internal validity of the experiment is compromised It becomes difficult to definitively attribute changes in the dependent variable functional communication solely to the current independent variable as the residual effects of the previous intervention might be confounding the results Therefore when theres a strong likelihood of such interaction or contamination an ATD is not the most appropriate design Other options represent either the strengths of an ATD rapid evaluation of multiple interventions or reasons for using different designs eg multiple baseline for multiple settings reversalwithdrawal design for demonstrating experimental control through removalreintroduction