Why are interviews with relatives and friends not always reliable sources in a retrospective analysis

Because sometimes when someone you're close to is being interviewed, they may shape their opinions or not give fully honest answers in order to try and sound like something you'd agree with.

answer; calendar;

i believe the answer is: description

description refers to the goal of psychologist to identify the phenomenon that being observed. this goal is being actualized by collecting data/information from various clues that observed through the phenomenon. this goal must be accomplished before pyschologist able to create methods of treatment.