Given McCain's VP choice, it would be useful to know the histogram of outcomes, especially during the first four years. If the risk of death or incapacitation is even a few percent during the first year, that would seem worth taking into account if you have any concern that Palin may not be quite ready to be commander-in-chief.
But, given the erratic, whimsy, capricious way in which McCain chose his running mate, I wonder which of the two - McCain or Palin - is less ready to be commander-in-chief. At least Palin would presumably be aware of her own unreadiness and hence willing to listen to the more knowledgeable advisers. McCain, on the other hand, has already proven that he couldn't care less about the wisdom of his own decisions.