Wrong, again.
The survey consists of telephone interviews with a nationally representative sample of 8,000 U.S. women and 8,000 U.S. men about their experiences with intimate partner violence.
http://www.vawnet.org/Intersections/GeneralResearch/NIJ_IPV.php
Not quite. Although this survey is advertised as "nationally representative," the study had actually very a shoddy sampling method, resulting in a very poor response rate of 56% (64% for women and only 52% for men). [Source: TJADEN, P. & THOENNES, N. (2000a) Prevalence and Consequences of Male -to-Female and Female-to-Male Intimate Partner Violence as Measured by the National Violence Against Women Survey, Violence Against Women, 6(2):142-161.]
Thus the survey's numbers only provide a rough estimate of prevelance of victimization, not a precise one.