One of WAVEs more recent posts was a study claiming that:
"Workplaces where guns were specifically permitted were 5 to 7 times more likely to be the site of a worker homicide relative to those where all weapons were prohibited."
Study at:
http://ajph.aphapublications.org/cgi/content/full/95/5/830
They started with 296 workplaces, and found 264 had explicit policies either for or against. (So they're excluding about 11% of their respondants right up front.)
The study admits that they ignored places where the person answering questions responded either "we don't have a policy about weapons" or "I don't know the policy". They only focussed on "weapons are allowed" and "weapons are prohibited".
Also, they weren't even studying whether it was the employees who were killing:
"The design of the study facilitated examination of workplace-level policies
but did not allow for questions about individuals, such as whether employees brought weapons to work and whether workers’ weapons were used in violent events."
"workplaces at highest risk for crime also might be those most likely to allow guns."
"We generally did not know how often employees had guns at work, whether workers’ guns were used during the fatal events, and whether perpetrators came armed or used the victims’ own weapons."
It looks like a case of someone starting out knowing what they want to prove, and finding data to support it. They ignore data that might disprove their theory.
If this is the flawed reasoning WAVE uses to support itself, eventually the truth will come out and they'll go away.