The main idea that the group decided to explore was whether there is a difference in Citibike usage on weekends. Prior to this, each member of the team had slight differences in the specific questions and hypothesis formulated.  We made sure to merge the thoughts and ideas into one consistent question and hypothesis, after factoring into considerations the feedbacks received from the 3 reviewers (Dr Bianco, Amber and Mark). 
As a result, the finalized question is on whether Citibike users are more likely to ride on Saturdays than Sundays. Some underlying potential rationale is that there are more places of interests closed on Sundays than Saturdays. Sundays are typically worship days where people go to the church too. Hence, it would be interesting to see if that might correlate in any way with the ridership of Citibike.