Final answer:
The primary purpose of a public service announcement about changes in waste management collection dates is to inform residents. It provides essential information necessary for them to adjust to new schedules and maintain proper waste management.
Step-by-step explanation:
The main purpose of a public service message notifying residents of the changes in waste management collection dates is to inform. When defining the purpose of writing, it's important to discern whether the aim is to persuade, entertain, or inform the audience. In this scenario, the author's intent is to provide essential information regarding service schedule changes that residents need to be aware of in order to adjust their behavior accordingly. This informative approach ensures that the residents are well-equipped with knowledge to help them comply with the new collection schedule, avoiding potential confusion or disruption in waste management services.