intransitive senses : to work as a factor
transitive senses
1 : to resolve into factors
2 a : to include or admit as a factor -- used with in or into
<factor inflation into our calculations> b : to exclude as a factor
-- used with out

2a) is the sense used in my previous: any analysis you do should be transparent to, but factored into, your reply. I think the distinction is that we don't "factorize" in math in the US. This is why (at the link) the writer was chastised for using a crude Americanism. (I'm just factoring here. :)

http://members.aol.com/tsuwm/