Cristián is a teacher in a program for children with autism. He is working with one boy and wants to see whether using a good-behavior sticker system will be effective for reducing his particular problem behavior. He begins by noting the boy's problem behavior for a week before beginning the sticker system. Then he tries using the sticker system for 2 weeks and notices a drop in the boy's problem behavior. For the next 2 weeks after that, he discontinues the sticker system and notes an increase in the boy's problem behavior.
What kind of design is Cristián using to test this intervention?