It's difficult to show a perfect cause-and-effect relationship when it comes to migration patterns, as individuals and families move for a wide range of reasons.
His defense lawyer said authorities set out from the beginning to link texting to the crash, a cause-and-effect relationship that he contends is not valid.
In his decision, Sixth Circuit Judge Jeffrey Sutton elegantly explains the difference between how a doctor looks at the cause-and-effect relationship and how the courts should do it.
While the study did indeed identify a striking correlation, researchers were unclear what actually drove this cause-and-effect relationship, with skeptics pointing out that a number of factors may have caused this link which were uncontrolled for in the study.
Retrospective analysis should not be the basis of an FDA approval, of course, but it can and should be the basis to understand direction and general magnitude of an underlying cause-effect relationship, particularly when that relationship is already is well established i.e.