By Richard Horgan Los Angeles (Knewz) — Even though post-traumatic stress disorder, or PTSD, is a serious consequence of military service, Americans are far off the mark when it comes to how many veterans are affected. According to a “Veterans Day Pop Quiz” field to 2,000 U.S. adults by The Harris Poll on behalf of non-profit Cohen Veterans Network, 55 percent believe a majority of veterans experience PTSD. The truth is, the figure is anywhere from 11 to 20 percent for Afghanistan and Iraq veterans, and right around the middle of that range, 15 percent, for Vietnam veterans. Another question t…