4. Conclusions

'Customer' are more likely than 'Subscriber' to use CitiBike during working hours. It might be because most of the 'Customer' are tourists, while most of the 'Subscriber' are local labor force. During working hours, a higher proportion of 'Subscriber' are staying in office, while 'Customer' are touring in the city.
The implication is that if we want to do advertisement targeting the 'Customer', the best time to display the advertisement would be the working hours because a higher proportion of 'Customer' can see the advertisement, while a lower portion of 'Subscriber' will be disturbed by useless information as for them. Regarding the types of advertisement, promotion for annual membership would not be a good choice, because most of the 'Customer' are temporally visiting. Instead, promotions about short time discount might be feasible, such as the one-day or three-day pass.
The weakness of this analysis is that we did not consider the seasonality. The conclusion we drew based on data of January might not able to apply to Summer.