that on-side kick was not risky-- according to the numbers

It was certainly risky in terms of what people would say.

But here are some interesting stats from Reed Albergotti in the WSJ...

New Orleans kicker Thomas Morstead squibbed the ball short in a surprise attempt at an onside kick and the ball was recovered by New Orleans....A day later, the trick play by coach Sean Payton was being touted as the gutsiest call in Super Bowl history.

But was it really that gutsy? The numbers say no. Statistically, the surprise onside kick works more often than not. Since 2000, onside kicks in the first three quarters—when they are typically unexpected—have been recovered by the kicking team almost 59% of the time. By contrast, 15% of fourth-quarter onside kicks were recovered in that same span.

In other words, it was more of a calculated risk than a gamble. A third-quarter onside kick is just a much more obvious risk than, say, blitzing a safety and a linebacker....