1. 
[syn: robustness, hardiness, lustiness, validity]
2.  the characteristic of being strong enough to withstand intellectual challenge; 
- Example: "the lack of robustness in the findings may be due to the small size of the sample"
The Collaborative International Dictionary of English v.0.48:
Robustness \Ro*bust"ness\, n.
   The quality or state of being robust.
   [1913 Webster]
WordNet (r) 3.0 (2006):
robustness
    n 1: the property of being strong and healthy in constitution
         [syn: robustness, hardiness, lustiness, validity]
    2: the characteristic of being strong enough to withstand
       intellectual challenge; "the lack of robustness in the
       findings may be due to the small size of the sample"