Thank you for the opportunity to help you with your question!
The main idea behind the Hawthorne study/effect is that participants in a survey/study will change their behavior on purpose because they know they're being observed. Think of it this way, if you are trying to study a group of workers in a kitchen and record how many times they wash their hands, go to the bathroom, etc. , then they might wash their hands more frequently than they normally do because they know you're watching them.
Please let me know if you need any clarification. I'm always happy to answer your questions.