Open a S&Q clip in your edit application and look at the data rate. It will be 35Mb/s give or take a little, whatever the frame rate you shot at. So for a shot that plays back 30fps with a bit rate of 35Mb/s if it was shoot at 60fps then as it as it was recorded at double the playback frame rate then the record bit rate must also be doubled.

Better yet, take the size of the file in megabytes, multiply by 8 (the number of bits in a byte) and divide by the number of seconds it plays back and see if the result is around 35, 70, or perhaps 14 (i.e., 35/2.5).

There is some overhead (the MPEG headers), so the result may be slightly less than the theoretical numbers. Nevertheless, it should be close to one of those values.