Effective writing does exactly what the author wants it to do. If you want them to laugh, then effective writing will make it happen. If you want them to cry, or be scared, or be stunned by your use of language, your writing is effective if it gets that result.
When I'm looking at student work, I'm looking to see how effective it is. Is it doing what the author intends it to do? If, for example, it's fantasy I might be looking to see how effective the author is at creating the milieu of the invented world. If it's a thriller, I'll be checking to see that there's tension running through each sentence and that the pace is right. If it was a more literary piece of writing, I'd be looking at the effectiveness of the language and character creation.
Writing is all about communicating. You have an idea or a story, and you want to pass it across to me. Because we're not telepathic, we have to use writing as an interface between our imaginations. The more clearly your idea or story is expressed on the page, the more easily it reaches me.
Tell me this story you have in your head, about these characters. If I understand it just the way you intended then your writing is effective. If I get out of it just what you wanted me to do, then it's effective.
I think writing has to be judged by its own standards. Does it achieve what it set out to do? Not good, not bad, but effective.