Interesting stats of class attendance

The data that I am sharing is from class attendance of 60 students in last 10 days in one of the lectures.

Roll nos         Average Absentees
1-12             0.7
13-24           0.8
25-36           1.1
37-48           1.6
49-60           2.6


As a trend you can clearly see that with increasing roll nos chances of persons being absent increase. And as an aberration you would see a sudden increase in 49-60 range. Well Guess what could be the reason for this behaviour??

It is that roll no 1-12 live on ground floor and 13-24 on first floor and so on. Well Aberration of 1.6-> 2.6 can be explained as it is 4th floor where lift does not work sometimes and it is the highest floor. Is the statistics not interesting??