Polygraph Questions

Hi all, I’m in PNW and going through the hiring steps for 911 dispatch (police only). I have a friend that works in the dispatch center that’s given some great advice. She says to just be honest with EVERYTHING. I need to complete a Personal History Statement (PHS) and as long as things move along, I’ll of course need to do a background check and polygraph. I’m concerned that my nervousness during the polygraph will prompt deceptive answering, or that I’ll recall an answer that’s slightly different than something on my record. Are polygraph questions based on background check info, as well as info you filled out in your PHS? Are they looking for consistency as well as deception?

TLDR: curious if polygraph questions are based on background check and info given in my PHS. Are there any tips going into the session?