Up to this point, we have been judging slope and level separately. But in the real world, you will want to evaluate whether an intervention might have changed the slope or the level of the behavior, which is called a basic effect. Remember from the first lesson that the basic effect must be replicated to have evidence that the intervention did cause the change!
When we’re comparing two phases to see if there is a basic effect, all combinations of changes and lack of changes are possible. A basic effect can consist of a slope change and a level change, as in this graph.