I have a device which obtains velocity based values over a period of 1 minute (average). I also have another device with which I am comparing that device. Now the velocity values can be quite random, but both devices should be similar in terms of increase or decrease within each minute: essentially they should have the same flow.

I saw online that some research has utilized the Pearson correlation to compare these values, but what I'm wondering is why? I read that this correlation only works for linear based values, and from what I read up, the velocities themselves were quite random (although similar in terms of devices). Or at least I don't think they are linear.

(cross posted from: http://math.stackexchange.com/questions/1018355/pearson-correlation-of-acclerometer-values)