NASA can't quantify Ice debris threat?

Apparently big behemoth NASA can't get their stats right:

"It's a really complex formulation, going from how much ice can you have on the spacecraft and what velocities, at what vibration levels it shakes loose, how big are the pieces that shake loose and then how they transport through the aerodynamic environment," he said.

"And then, what's the resistance of the tiles to ice impacts and finally, given an ice crater - which is different from a foam (insulation) crater - how well can we enter (the atmosphere) with regard to that?

"The uncertainties in each of those areas are significant," he said. "There are all sorts of numbers that are floating around. We have nine different estimates for ice on tile from one ice location. ... It is a very complex problem.

"So what we did was, we looked at the relative risks and we're convinced the ... the remaining risks due to ice is around an order of magnitude less than the ones that we fixed."
Muratore said ice represents more of a threat to the shuttle's tiles than it does to its reinforced carbon carbon leading edge panels and that even though engineers used "all the supercomputers at NASA to run it down ... it doesn't lend itself to a single number."

"Impact dynamics are a very complicated engineering discipline," he said.

While he would not discuss the statistics underlying today's "go" recommendation, sources said some estimates of the likelihood of tile damage due to ice impacts - damage that would require repair or some other response - could be as high as 1-in-100 or so or as low as one in tens of thousands, depending on the assumptions that were made.

So in a nutshell they don't know what threat ice debris has on the shuttle in quantifiable terms... Or do they? What about the analysis that was done weeks ago that showed a much higher than acceptable risk of debris that was brushed away as being to armagedonish by NASA officials? The stories they are a changing. Joe Blow Astronaut must be scratching his head while simultaneously crapping his pants listening to the nerds give him updates on the ice debris risk situation. So what does NASA do when it don't know? It gives the green light:

"At the end of the day, the recommendation ... was that we're in an acceptable risk posture and they recommended to me, the program manager, that we proceed on with the launch," said shuttle chief Bill Parsons. "I accepted that recommendation. And that's where we're headed now."

Wait didn't they just say that impact dynamics was too complicated to know the risk. So it's an acceptable level of risk, which we don't know the actual risk, but it's an acceptable risk... Although we don't know the risk, it's still an acceptable risk. Anybody else confused?

"We believe it's an acceptable risk at this time," Parsons said.

Is not scheduling a second ET fueling test an acceptable risk? NASA engineers requested it to ensure that the Hydrogen fuel level sensors were operating correctly after they showed to be working intermitently. There are many ways that a vehicle like the shuttle can go kaboom. You'd figure the thought would endeavour a little more willingness to go the extra mile to allieviate some of these oustanding issues.