The candidate chosen probably had the least work experience among the seven interviewed and 5 who went through our "Apprentice" style one day practical workout with us.
While the basis within which the person was chosen is highly situational to my team scenario I want to highlight few points in general that we were looking at.
a) Capacity to do what you have to day in day out (both technical and soft skills)
b) Ability to learn and expand capacity to take on bigger projects/roles within the team
c) Cultural fit to the team (More importantly are there any disconnects that might lead to team synergy) and this should be mutual. A day out tells you a lot more than controlled interview environment
d) What the person brings to the table to add value to the team! (Skills, style etc)
e) How comfortable is the person with the work set up and people the person will work in the future (from office set ups to lunch rooms and toilets the person will have to be comfortable!)
The process becomes much easier if you share your expectations with the prospective candidates. Before asking them to come for a 'day work out' with us as part of the third stage of the interview I shared with each one of them why we're doing it and the importance of the same. They too become comfortable with the process as it gives them an opportunity to evaluate to a greater extent the 'fit' in their own terms. While the work they might have to do might be structured in such a way to represent a typical day in the life at office, as much as possible avoid stage drama!