Through any three non-collinear points, there exists exactly one plane. A plane contains at least three non-collinear points. If two points lie in a plane, then the line containing them lies in the plane.
Since the statement given in the question is "Four given noncollinear points are contained in a single plane.", since three non-collinear points creates one plane, the fourth point could be contained on the plane or not, therefore, this statement is sometimes true.