Final answer:
Emily is on a fixed interval schedule of reinforcement, where she gets a star sticker on a fixed weekly basis for good performance on her spelling tests.
Step-by-step explanation:
The schedule of reinforcement being used for Emily, who receives a star sticker every Friday for a spelling test, is a fixed interval schedule. This is because the reinforcement (star sticker) is given at a fixed time interval, which is every Friday following a spelling test, assuming she performs well. This type of schedule reinforces behavior after a set period of time has passed and the desired behavior has occurred.