Interface MPL3115A2 with an Arduino micro-controller

Hello, I want to hook up a MPL3115A2 pressure transducer sensor and interface it with an Arduino micro-controller. But I have a question. I could set up the display and I can see it is working. The problem is that I get some random numbers, regardless of connecting the sensor or disconnecting the Arduino analog input from it. What might be the problem? Even when nothing is connected to the A0 or any other analog pin, I see the same behaviour.
I appreciate any reply and help.