Hi I was wondering if any one can help as fairly new to this. I am trying to establish if there is a significant difference observed between the concentration index in 2 different years (ie CI in 2013 and in 2015) and I'm really struggling. I just wanted to know if that was possible and if so how. Just to break it down I have calculated 2 concentration index in different year and Now i just want to calculate if the observed difference overtime is significant. I would be grateful for any help.

Many Thanks