There are two sides --- as Abigail-II mentions, incorrect responses require additional resources for correction and run the risk of the answer being used before it is corrected. That, of course, applies to all incorrect --- or suboptimal --- responses, not just those posted be relative newcomers.

On the other hand, as moxliukas and Molt mention, many times an incorrect or suboptimal response will generate corrective followups that are more generally instructive to more people in the long run than a simple correct answer alone would have been.

Personally, I fall into the second camp. That doesn't mean I support total guesswork, or posting things that haven't been at least minimally tested --- but I do not think 100% certainty should be a requirement for answering. About the only thing I am 100% certain of is my own fallibility.