Academics are curious people. They are driven by questions. They assume their fellow academics are also curious. Consequently, we often write things as though it’s a detective novel.
Everything start with questions. You see posters that have question in the title, questions in the introduction, questions leading off the results... and everything is revealed at the end.
It’s just like in a detective novel where all the clues are laid out, the suspects are gathered, then the big revelation: “The butler did it!”, so to speak.
I contend that it is much better to make statements than ask questions on a poster.
Always remember this: in poster sessions, there are always more posters than time to view them. And questions are more work for the reader than statements. I have to understand the question, then see the evidence, get to the answer, and check that the evidence and the answer line up. Now, these are good practices... but they are time consuming. Respect people’s time and tell them the bottom line right away.
This need not make for a disappointing story. If you go back to detective fiction, one famed detective series made it a point of revealing the killer at the start of every episode:
The question in Columbo was not “Whodunnit?” but “How’s he gonna prove it?” The fun in Columbo was in watching the cat and mouse dynamic between the detective and the murderer, and seeing the killer try to answer the infamous “Just one more thing” question that Columbo was always asking.
Update, 20 July 2016: There’s now research data that supports this method! “Positive framing” in a title (as the paper calls it) was associated with more online attention than questions or generic statements.