Introduction - a short introduction that explains what citibike is and why your question is interesting. Normally this would also include a discussion of similar work previously done (a literature review) but you do not have to worry about it now.
Citibike is a bicycle sharing system open to subscribers and non-subscribers. For non-subscribers, a daily pass will cost $12, whereas for subscribers, a monthly pass cost only $14.95. Given the way the pricing system is set up, the idea is that the number of non-subscribers (customers) using citibike is likely to be significantly less than subscribers who have committed to a monthly or annual pass. However, it will be interesting to understand the travel patterns of customers and subscribers, by looking at citibike usage by these two groups during the weekdays and weekends. This will allow us to better understand how different user types use citibike across the week. Therefore, this paper aims to test the hypothesis that the ratio of customers riding over the weekend to weekday is the same or less than the ratio of subscribers riding on weekends over weekday, at the significance level of 0.05.